But then again, since you’re taking his ridiculous casus belli scribblings at a face value, there’s little I can do to convince you.
Similarly, it makes sense that he would selfishly prefer to be historically remembered as the guy who unified Russia, Belarus, and Ukraine, rather than the most successful thief after the fall of communism. The citizens of Ukraine (and probably also Belarus) are not happy about it, but I guess the idea is that after being conquered and brainwashed and all dissidents thrown in jail, maybe their grandchildren will feel like happy patriots of the Greater Russia -- and if they won't, well, it's not like in Russia anyone actually cares about what people think (unless it is telling them what to think).
The citizens of Belarus have way less freedom of speech than even Russia, let alone Ukraine that's relatively free since 2014.
Russia has had, until recently, some forms of freedom of speech, at least on paper, while Belarus has none of that, not even on paper.
Putin wishes he had the authoritarian powers Lukashenko has in Belarus where he's been the sole dictator for the past 26 years.
Putin is basically a dictator but still has to go through a bunch of red tape to stay in power and pretend he's there though democratic elections and what not, while Lukashenko doesn't need to do any of that BS in Belarus, he's an absolute savage who doesn't even believe COVID is real and says "being a dictator is fine since it's better than being a homosexual".
So good luck being unhappy in Belarus and doing something about it.
Putin isn't a startup founder. The man has no interest in leaving Russia and if you go and read his piece on the question of Ukrainian and Russian statehood[1] it's very clear that to him, Ukraine has historical and even spiritual significance. Going all the way back to the Kievan Rus he sees the three peoples of Belarus, Ukraine and Russia as inseparable and the emergence of, in his view, 'anti-Russian Russia' in Ukraine as a red line.
And I don't know why people keep this 'the world's richest man' meme alive but just because he always tolerated the oligarchs as a support structure for the state there was never any indication he cared a single bit about money. He always had aspirations to restore Russia to a great power, quite openly.
[1]http://en.kremlin.ru/events/president/news/66181