Cornered from seizing crimea in 2014 and creating/supporting two Donbas breakaway regions?
I don’t think he was cornered at all, just impatient. He’s 70 years old and the conflict had frozen for 8 years. Barely anyone even cared in western europe/US. That’s perfect for Russia! But can he really live for much longer? He may not think he has many more years to dedicate to the task.
Now the invasion has completely backfired and he is in a political corner he backed himself into. If your theory of Russian machismo is correct, he can’t back down from trying to beat up a smaller weaker country - and he simply can’t beat them.
So he has to lose in Ukraine, beat the first coup, and consolidate power simultaneously. I believe Putin will be just like Erdogan who used the 2016 “coup” to eliminate political enemies.
People died in Turkey in 2016, there was damage- but Erdogan emerged stronger and won subsequent elections. Maybe there will be Russian proscription lists and purges now.