But aside that - for all the usual power reasons. Distract fromm inner problems, covid, economy, opposition, ...
It's only economical suicide if the West makes it so, which it most probably would not - and then there is the question if that would be enough. What if China is able to provide whatever the West would not. Moreover, Russia has close to no debt and high currency reseerves. It is true that it mostly sells oil, gas and minerals, but there are enough buyers for that.
In short, maybe their calclulus is very different to ours.
I'm mostly thinking international politics and -projects like Nord Stream 2. But even internally, there are already anti-establishment movements in Russia. Unpopular military intervention might be grist to the mill for them. I don't think Putin wants to risk a situation like in Belarus a few months ago. It's easier to govern if the people don't openly disapprove of you, even in a dictatorship.
> It's only economical suicide if the West makes it so, which it most probably would not
I remember plans about excluding Russia from SWIFT. I don't know if that is still on the table.
If Russia amasses several hundred thousand troops on Ukraines doorstep that’s not a supposed threat, it’s a threat since it’s perceived as a threat. Pointing a gun at someone is a threat. It’s not a supposed threat.
Also: The Russian invasion and occupation started 8 years ago!
They did invade: Crimea and Eastern Ukraine. Was not a suicide for Putin, quite contrary, his political position within Russia has greatly improved.
They occupied the territory first and then conducted the "referendum" to make it "legal". Don't buy this horsesht.
Ok stop. This isn’t intellectually honest argumentation.
There have not been any free/observed/internationally recognized referendums on Crimea. Most importantly, the referendum wasn't with blessing from Kyiv.
There was an annexaction which was partially done with military means and partially through a mock referendum. Both of those are blatant attacks on Ukrainian soverieignty.