Regardless of what it’s becoming now, the invasion was not initially about pain and fear. Putin wants Ukraine as either a vassal or part of greater Russia, and he wants NATO weakened or destroyed. I think he thought Ukraine was going to roll over fairly quickly, and he’d even hoped they’d be able to do it without actually invading. Had Ukraine been conquered quickly and/or without an invasion, it might have driven a wedge between NATO members.
At this point, though, Ukraine is not rolling over, NATO has been revitalized and Putin has backed himself into a corner. Causing pain and fear is what he has left. Yes, Ukraine will likely fall in the near future, but good luck governing it. It’s gonna be little more than a drain on what’s left of the Russian economy.
Causing pain and fear in Ukraine doesn’t actually help him at home, either. Sure, odds are fair he can keep everything clamped down, but lots of Russians have ties with people in Ukraine. This doesn’t make things easier for him.
He lost his best chance to destroy NATO when Trump lost the 2020 election, and at this point I think he’s gone all in and his playing all his cards. The problem is that his hand just isn’t that good.