The decision-making involved was quite rational if you assume Putin was operating with incomplete information. Had the war ended in two weeks, as it looked like it was going to right at the start, he would have met his domestic goals.
But then it turned out that Ukraine was more prepared than Russian intelligence thought, and Europe started flooding it with weapons. Given that Russia isn't taking the war half as seriously[1] as Ukraine is, none of what's happening is irrational or surprising.
[1] By design. Putin didn't want an existential conflict that required actual sacrifice on the part of his constituents, he just wanted an easy victory to cement his popularity. He's now stuck in a situation where he has few good options.
But then it turned out that Ukraine was more prepared than Russian intelligence thought, and Europe started flooding it with weapons. Given that Russia isn't taking the war half as seriously[1] as Ukraine is, none of what's happening is irrational or surprising.
[1] By design. Putin didn't want an existential conflict that required actual sacrifice on the part of his constituents, he just wanted an easy victory to cement his popularity. He's now stuck in a situation where he has few good options.