i guess (yes, these are NOT facts) that steam has guidelines that he doesn't like for what the game has to provide (especially since it has an implemented workshop, steamworks DRM etc etc) and valve takes a big part of money from sales, so the profit margin is probably bigger on the russian platform.
also i'm pretty sure Pavel doesn't like that people put non-russian trucks and pickups on his game, literally all the mods added to the other version are soviet/russian vehicles
another theory is that the mail.ru version is published without oovee's permission and it's a big **** you to oovee to take the russian income/market from them
even though i know these are not the real reasons why he is doing this, and even if they where, he needs to get the hell over himself and except the fact that "These mods he doesn't like" has been keeping his hack job of a game afloat for the past, what? 3 years now, OOVEE NEEDS to throw a lawsuit against his D**ba** for selling OOVEE's game on another website. I wouldn't be surprised at this point if he was doing this without permission.