I don’t think he’s senile/mad/crazy. I think he’s getting worse with age, as we all tend to do, and he believes that Russia needs to control Ukraine, either openly or not. Bear in mind the Euromaidan appears to have caught everyone flat-footed, in that Ukraine was just as corrupt as say, Belarus, and there was an uprising that no-one expected. The only way for Putin to understand a popular uprising is that it was caused by NATO/EU/The West. This is also the only way tankies in the West understand it, the Ukrainian people themselves have no volition, it’s just NATO forcing them to do what they want (tankies also believe Russia is still communist). Prior to that, Ukraine was safely under Russian influence, because Putin doesn’t count countries as ‘buffer’ zones unless they’re also under his thumb.
Putin wasn’t counting on any serious NATO support; it’s clear to me that NATO has done almost everything short of militarily joining in. The supply of arms means the Russian superiority in armour is blunted, and their dominance of the skies is partial at best. NATO is obviously sharing intel with Ukraine, and the publicity before the invasion obviously made a lot of “Putin won’t invade.” takes look like absolute shit, when it happened. Putin definitely wasn’t counting on widespread sanctions, nor was he counting on the EU reacting within a matter of days. The EU response to this has been shockingly fast.
In an ideal world, for Putin, there would have been a Trump re-election, and the US would have either left NATO, or done nothing at all and made sure NATO response from other countries was minimal.
Barring a major change, frustration will set in and Russia will use more artillery fires on civilians, and attempt to blunt-force their way in to Kyiv. They will take horrendous casualties, but unless something major changes, they will succeed eventually, at tremendous cost. They are currently pausing to replenish, but that won’t last, and Putin will put the boot in on those who fail to perform. The bombing and shelling of Kyiv will be tremendous, I don’t think they have the troops to take it. I’m seeing a lot of dead VDV troops on social media; likely because common infantry conscripts cannot or will not perform, overuse of better quality troops is occurring, and they’re taking disproportionate casualties, making the problem worse.
Ukraine will be bounced into the EU in record time at this rate, and after perhaps another partition, the remainder will find itself in NATO.