NEP was a thing though. Very limited and tightly controlled, but possible. Both NEPmen and foreign capitalists had a brief window while economy was healing.

https://en.m.wikipedia.org/wiki/NEPman

https://en.m.wikipedia.org/wiki/Foreign_concessions_in_the_USSR

I don't think one could be safe throwing them around like that though. Being big probably meant you have a particular relationship with local administration who don't find you too capitalistic.