The latter part is true, but the former is somewhat unclear I think. Or at least, I’m not sure if it’s actually been pinned down that well.
The problem is that “Arab” is both an ethnic group, but one which isn’t very distinctive from many other ethnic groups in the Middle East, and it is also a cultural heading claimed by many more-or-less unrelated ethnic groups. The leader of the Umayyads was Syrian, and I think his forces sort of recruited as they went along.
During the Jewish “Golden Age” in Spain, Jews had to wear identifying marks, and step off the sidewalk to let a Muslim pass.
Actually, they did expect it… 
The Spanish inquisition always gave you 30 days notice.
Stephen Fry in QI explaining how they gave the accused time to prepare, no warranties that you would not be tortured if they did not like the answers you gave them. And those found guilty after the 30 days elapsed could be burned at the stake. And yes, like many dictators did in the 20th century with their enemies the Spanish rulers then could spare you if you ratted the Jews or Muslims that in reality were not Christians but that they had converted "fraudulently".Lots of property and goods would end up for the church or the government. So, it sadly led to a lot of finger pointing and “confessions”.
True, but that was relatively speaking a late development. Well, mid-period anyway - the Muslim conquest dates from ~711 and the harsh revivalist movements of the al-Murabitun ( Almoravids ) and the later al-Muwahiddun ( Almohades ) who sequentially displaced them didn’t arrive on the scene until 1086, when Muslim Spain was already in decline. Indeed they were invited in because the relatively tolerant taifa states were on the ropes. So any conversion curve had already about reached its peak before they came along with their brand of purist zealotry. I’m sure they didn’t help matters any, but at worst their intolerance perhaps might have accelerated the retreat of an already declining faith.
Yeah, they didn’t exactly cover themselves with glory. Although details are really murky, the resistance does come off as particularly half-hearted at best. The only really major field engagement seems to have involved a serious defection in the ranks and communities and local rulers seem to have fallen over themselves to come to quick accommodation with the invaders. ( and in fact some traditions think they might have actually been called in by one side in an ongoing internal political schism ).
I’m not sure it would be fair to characterize Visigothic Spain as being ineffectual throughout its whole history. But the political infighting seems to have become become exceptionally toxic at a very bad time.
I recall from Gibbon that the Arabs were initially invited in by one Count Julian who had some sort of beef with the Visigothic king and that when a small expeditionary force had found Julian true to his word the main body of Arabs under Tarik sailed over and went through Spain like a hot knife through butter because, as said above, the Visigoths were totally disunited in spite of their overwhelming numbers. Do modern historians still accept the story of Count Julian?
Yet go beyond its borders to areas of Serbia and Croatia that were just as intensely occupied by the Turks, and try to find a mosque, madrasa or any other sign of the Turkish period.
We are aware of the most recent shameful period of ‘ethnic cleansing’, but there is also a long, long history of systematically erasing all physical evidence of the Muslim presence in these areas.
Spain to its credit retains a legacy of the most beautiful and artful Islamic architecture.
To revert to the OP’s question: for centuries after the Inquisition had been at work, Spain wasn’t, as much for economic as for any other reasons, a country many people would have wanted to immigrate to, especially by the time when travel from its remaining Muslim colonies might have been starting to become a practical possibility, and when Spain finally joined the EU, it was hardly an economic magnet by comparison with countries further north, where there were already established communities from North Africa and elsewhere.
Spanish, currently living in Spain. I used to live in the US (4 years in Miami, back to Spain, 1 year based in Philly jumping all over the continent) and often work abroad, so while not as widely traveled as some other posters I can criticise the Customs agents of a couple dozen countries
Another factor is that the kind of people who will switch religion for economic or social profit were as quick to switch in one direction as in the other.
What Dark Ages? That’s so 20th C.
The Chinese invented a lot of stuff, though. Gunpowder, spectacles, paper, the compass… the real question is why China suddenly stopped being the leading light in invention and discovery, IMHO.
They didn’t have the Protestant Ethic?
No. It is a latter myth.
Probably. There have been attempts to tease out identities and like the Arthur myth in Britain there may be some real individual hiding back there, with some real political machination going on. But since there is essentially no good contemporary evidence for much of anything in that period, it is certainly correct to say it should be taken with a hearty handful of salt.
Ooh! Ooh! I know this one, or at least I have an answer for it. A theory that I’ve heard is that one of the big ‘game-changing inventions’ was glass, because you need glass for microscopes (and thus germ theory) and for telescopes (and thus astronomy and navigation) and for glass beakers (and thus chemistry). Europeans were experienced in handling glass, and thus able to create very fine lenses, because they had a whole trade of glass-makers who made beautiful drinking cups. The Chinese didn’t have any reason to develop the trade of glass-making, because they had extremely good porcelain cups. Since they didn’t muck around with glass cups, they never got to glass lenses.
At least, I learned this on QI.
So if there were some mass conversions, would there be mosques in every village (as there seems to be with churches?) If so - were they torn down, or repurposed and the original design is still apparent, etc.? Or did they simply repurpose Christian churches?
That’s where I learned it too. The Chinese invented sunglasses using smokey dark quartz, and the Inuit invented snow googles with little slits to see though, but neither worked with glass corrective lenses.
Not necessarily every village, but they would have been common.
All of the above, I’m sure. One major example in Spain is the Mezquita in Cordoba. Started as a church, became a dual church-mosque after the conquest, then rebuilt as pure mosque, then converted back to a church. Wouldn’t be shocked if the site started as a Roman temple or some other pagan site as well ;), though that is certainly pure speculation.
ETA: Worth a visit by the way - very impressive structure internally.
Yes, thanks. I’m just wondering if this is something common, that a lot of minor towns and villages still have evidence of mosques of some sort instead of parish churches.
The Cathedral of Cordoba used to be the Mosque of Cordoba, which was built atop the destroyed Visigoth Cathedral of Cordoba which was built atop a temple which may have been dedicated to Diana (the dedication is speculation, but bits of the old temple that were found during some repairs are visible under a glass) which…
The Cathedral of Tudela used to be Cathedral, Mosque and Sinagogue (different parts with different entrances but with internal communication). The Mosque and Sinagogue parts got repurposed as offices and archives for centuries, now they’re part of the guided visit. The Sinagogue is much more obviously different than the Mosque.
The Mosque of Bab al-Mardum (مسجد باب المردوم, and I hope that’s correct because I just copy-pasted) in Toledo became the Ermita del Cristo de la Luz, Hermitage of Our Lord of Light.
Many others were destroyed, if just to reuse the land.
Current mosques generally aren’t purpose-built, they’re rented shopfronts or flats; if they can, they try to rent at least the shopfront and one of the flats above. This is common through the minority religions: JWs or Evangélicos (not to be confused with the American Evangelicals) are likely to do the same. It takes a lot less money and paperwork to rent a shopfront or even a whole building than to buy a piece of land and erect a specially-dedicated building.