how can we establish democratic peace if we don't bomb those russians and take over their land?

Barely anybody says that besides some uninteresting figures mentioning a ridiculous idea of balkanizing Russia... (Balkanize my balls).

But then, why did they vote for Putsin?

Putin isn't a legitimate leader who got honest public's vote. In reality most of Russians who are dependent to governmental institutions are forced to participate in the electoral apparatus for statistics' sake only. People just have to show up. There's various cases of fully discovered falsifications, independent spectatorship isn't allowed. The whole process is just shady, especially after "online vote" has been established, which has pretty non-trasperent protocol.

They aren't so different from the government, and if they hate it so much, just get out of there. not that difficult.

Unironically this, since the summer of 2021 Zelensky has been pushing for proper face-to-face negotiations with Vladimir Putin personally and was... Geopolitically ghosted. Zelensky was ready to make Pashinyan at the start of the war and basically... Give up Crimean region. Seeing all of the tactical and local failures of Russian military made it obvious that they weren't planning for long-term, full-scale attrition war that required full involvement and genuine contributions from society.

Why are people talking about international peace relations as if it can be achieved?

Modern humanity established certain systems throughout these two centuries, despite all of the internal contradictions of modern governments' development and longing for full-scale mobilized and militarized societies, we created mostly consistent precedents of geopolitical relations... Yes, they're hypocritical, yes, they're not fair and they left an irrational policeman with a huge propane baton in charge of our globalized economy, but at least they prevent consistent genocides, long-term attrition wars amongst European nations.

Didn't international peace cause Stalin and Nazi Germany to kill 10 trillion people?

Entirely backwards, Stalin and Nazi Germany killing 10 trillion people caused international peace.