Admiration for the USSR among English intellectuals predates WW2. So the answer to your question is in the social milieu of the 1920s-30s. Someone else will have to try a detailed explanation.
While this may be so — although I am sure there were enough intellectuals in both camps — it cannot explain the atmosphere that Orwell is describing:
> At this moment what is demanded by the prevailing orthodoxy is an uncritical admiration of Soviet Russia. Everyone knows this, nearly everyone acts on it. Any serious criticism of the Soviet régime, any disclosure of facts which the Soviet government would prefer to keep hidden, is next door to unprintable.
What is this prevailing orthodoxy? How has it been reached and maintained? What happens to dissenters? What enforces the unprintability of the criticism? To achieve such a level of control, full government and media support is necessary.
It's not difficult to see that the early Soviet Union was actually better on a number of dimensions over both the Tsars and the West on basic equality and humanity when comparing against the life of an Indian or an African American. It had decriminalized homosexuality and was arguably less anti-Semitic than the West. The trajectory was utopian... but it nosedived into Stalinism which was, well..., a nightmare.
The history of Russia is one of an endless parade of terrible leadership which invariably decides that a quick round of death squads will solve all the problems.
Their biggest effect was external: most welfare systems were started in the West in response to the observation that it was a bad look for capitalism if people were starving in the streets, whereas ultimately the USSR liked to pretend they fixed that while just doing it to the Ukrainians, Polish and other Baltic states.
No. Claiming this underplays how appalling Stalin was. Lenin purging Mensheviks AFAIK, meant losing party membership and maybe emigrating to continue your political project, whereas Stalin's Great Purge killed a million people. This isn't a defence of Lenin, it's just that Stalin was on a different level entirely.
> Their biggest effect was external: most welfare systems were started in the West in response to the observation that it was a bad look for capitalism
What? That's nonsense.
Forced labour camps and secret police organisations were pretty ubiquitous. The Tsars had The Okhrana, forced labour camps and political repression (Lenin, Trotsky and Stalin had all been exiled to Siberia). The Checka and Gulag were the Bolshevik versions of the same thing. Russia had the White Terror... and then the Red Terror. It all fucking sucks but the point remains, Stalin took things to new levels of psychopathic insanity where we start hitting 10s of millions of excess deaths.
If you don't like Gulags, then bear in mind they were created at roughly the same time the US setup forced labour camps in Haiti that led to 1000s of deaths and extra-judicial killings. Not something Americans talk about much. Should Woodrow Wilson be compared to Stalin too?
I don't know why I keep hoping mgmt will see that one day and decide not to have pretty bad things now that some later nutjob can turn into really especially bad things. It's not much of an up-side that the people who built the tools are often consumed by them.