The idea was put forward long before that, even in Britain - David Lloyd George was making noise about national health insurance and even unemployment insurance as early as 1908 or so.
The war made it all possible, though, partly by destroying much of the system in place and partly by encouraging people to “pull together” and all that. Even though it was popular in 1942, it would have been awfully difficult to turn it into policy (especially since Churchill didn’t think Britain could afford it).
The war made a lot of things possible. Some were good, like the welfare state, and some were not, like Milton Keynes.
So instead of having the stereotypical revolution, with the running and the burning and the backs against walls, we just had to have the major cities destroyed by a foreign power, major financial crisis and an over-abundance of war wounded. So things are looking up for the modern US, as his great loafy-meatiness said, “two out of three ain’t bad”.
WW1 probably had a bigger effect in establishing the welfare state than revolution.
The idea of UHC and the welfare state certainly predated this, Lloyd George and the Pensions vote, which in turn led to the Parliament Act and the limiting of the power of the House of Lords would be one very significant part of that.
The loss of a generation of landed gentry and their reactionary views, along with the idea of a ‘Land fit for Heroes’ at the end of WW1 is important.
WW1 seriously damaged the paternalistic view of the upper classes in the minds of the lower orders. I don’t think its Communism on its own that led to a more socialist outlook, WW1 pushed Russia over the edge, but then it also led to the Weimar republic and the later rise of Hitler, and also the rise of Mussolini. WW1 brought in huge social changes around Europe which had varying effects in each country.
In the UK, Socialism goes hand in hand with progress to unversal suffrage, many folk think that suffrage means the right to vote for women, it just means the right to vote.
Up until WW1, only 40% of males in the UK had this right, because this was tied to owning real estate - and this was deliberately done so to keep the lower orders out of politics.
The way that MPs were funded (ie not at all) ensured that only the wealthy or those with independant means could contemplate standing for parliament.
The rise of trade unions, whose membership then paid to fund MPs brought in more support for the Liberals, who then brought in the Parliament Act I have already mentioned.
It’s fair to say that this movement toward wider enfranchisement was already under way prior to WW1.
It wasn’t until 1918 that most of the population got to vote in a way that we could recognise as democratic in the modern sense. Even then there were still plenty of voting restrictions. WW1 certainly drove that process which had been under way but temporarily halted by that war.
By the end of the war, the great burden of casualties had been borne by men who did not have the right to vote and the survivors were seen as having a moral right since they had died to maitain the existance of the government.
It took a combination of labour organisation, which then funded socialist political parties - ILP and Labour, to expand the vote wider and to build up the ideas that enabled the Beveridge report to become policy.
I guess you can take many points in UK history and build up a progress toward our version of democracy and socialism, actually in the UK we don’t really think of ourselves as particularly socialist at all, more like capitalist with some social measures.