The government that oversees that particular lottery could pass a law tomorrow that says “sorry, we will now tax lottery proceeds at 99%”. The power of the purse is mighty.
Except that then the lottery would have nothing to make payouts with, so there would be no lottery. The government does get it’s cut, that’s what government sanctioned lotteries are for, and doubtless a lot of analysis goes into optimizing the revenue stream. ETA: now if a government were in such desperate straits that it was willing to eat its seed corn, then that could happen– once. But then a lot of people would have a lot more to worry about than lottery winners getting screwed over.
I have separated what a government will and will not do from what a government can and cannot do, for too many people confuse the latter with the former and end up very unpleasantly surprised.
I believe it is France that has the wealth tax, you must declare your net worth and pay X% each year. This is supposedly why it is unclear how much was stolen when thieves tunnelled into a Marseilles bank from the sewer and spent a holiday weekend breaking open safe deposit boxes. (“Safe”?) The story was a lot of rich people kept some of their wealth out of sight in these boxes rather than declare it.
I had an argument once with a local bigwig in the left-wing party (NDP) about the Beatles’ song Taxman where it’s “one for you, ♫ nineteen for me 'cause I’m the taxman…” he said the top marginal rate in the UK was never close to that high. I looked it up (hard before the internet) Apparently it was 83%. At the time, benefits were not taxed so it was for example, all around better for a company to provide their top people a car and chauffeur than to give them the equivalent raise.
As I understand, the problem in the mid-20th century was not wealth tax in the UK, it was estate taxes. Those giant ostentatious mansions from centuries past were valued highly, but did not themselves produce income - indeed, cost a lot to simply maintain. Many I gather have ended up with the National Trust, or open as tourist attractions. the lucky ones get features in TV and movies.