All in all, on average, primary source of info. Afaik, a lot of works goes into controlling which parts of internet are well accessible and which are not. The social networks and group chats are amplifier of what you see elsewhere. They don't bring new information from outside into debate. They are also reflection of what you consider appropriate or safe to share. And with new criminalization of "disinformation about war", it will be less.

And right now, as far as Russian official version is, afaik, Ukranians are nazi child killers and Russia is there to denazify and protect regions of it.

Moreover, ousting Putin requires more then unhappy disagreeing populace. It requires either super weak regime or internal coup of powerful players. Regime is not weak currently.

In the USA, there is nothing stopping you from going to learn all the pro-Trump, anti-vax, anti-mask propaganda you want, yet millions of people do not.

What makes you think it's any easier for someone to leave their filter bubble in Russia, where the consequences aren't just losing your job and social ingroup, but also being kidnapped, tortured, and being found dead in a ditch five years from now?

Like, who exactly?

If you mean Russia, they had years of internal violence behind them. They had well established revolutionary movements and terror groups acting inside on top of it even before WWI. And the regime was weak and forced to do concessions already in run up to WWI and even weaker by end of it. They were doing reforms, too little too late, but they were doing them because internal pressure was strong for years.

That revolution did not came out of nowhere. Plus, the population was literally hungry and desperate to large extend. And plus, it was followed by major civil war of like 5 sides competing for power.