Also, what better way to say "let's not nuke the shit out of each other" than to cooperate on civilian space programs?
The height of the cold war when we had thousands of nukes pointed at each others cities, multiple proxy wars including Vietnam, a conservative Republican president and conservative Communist premier, yet somehow a civilian international space program was still considered worth it.
The whole "for profit" thing just seems like such a sham. It's only "for profit" because the government is paying the bills, while avoiding liability and scrutiny if something goes wrong. Every space accident will now be like the Virgin Galactic fatalities, a bunch of secretive corporate NDAs instead of an open inquiry like Challenger.
I think a major reason was that, for all its failings, USSR was a superpower, powerful, influential, with an internationally attractive ideology. Russia today is a sunsetting power kicking around itself.
This applies to cultural contacts in general too. Every time the US decided to "punish" the Soviets by cutting back cultural contacts... breathtakingly stupid (IMO).