While I hesitate to speak on this topic, given that it’s already a super-contentious topic among historians (that’s saying alot) the best from what I can gather is that while Lenin agreed that Zionism is a disgusting ideology of racial supremacy, Lenin’s time had come and gone decades ago, and he more or less “served his purpose” in helping overthrow the Tsar and create the USSR.

Because of the tremendous horrors of the holocaust/WW2, my best estimation is that the USSR/Stalin felt that since many other ethnicities had their own “home country”, that opposing a home country for Jewish people would be hypocritical and wrong and lacking in empathy, and that if Jewish people didn’t deserve a secure home country, then no one did.

I think that Stalin’s support for the state of Israel was an example of what Stalin thought was pragmatic realpolitik, and would help the USSR be considered a potential ally and savior of Jews, and oppressed people across the world.

The Arab/Southwest Asian countries at the time were often repressive and reactionary dictatorships, that especially enjoyed the support of the U.S./Britain, and I can understand the genuine worry and concern that the West would inflame tensions to create a second holocaust and make Arabs into the bad guys and supremacists.

I think sympathize with Stalin’s decision, and I think that hindsight is 20/20. I’m not arab, I’m Latino. This is just my best guess.

I’m not an expert on the issue but just from applying common sense I’d imagine that coming out of the wake of WW2 and what the Nazis did to the jews that it just sounded like the morally right thing to do at the time. Similarly, it also seemed morally right at the time when Lenin, Stalin and Khrushchev gave territorial concessions to Ukraine after the legitimate oppression they faced under the Russian Empire and couldn’t of known what a mistake that would eventually be.