Re: TSMC is vital to China too
Eh? Plenty of people thought Putin would invade Ukraine.
Sevastopol is the only decent deep-water port in the Black Sea, which makes it the only decent military port near Russia with access to the Mediterranean and the Suez Canal. Without it, Russia's navy doesn't have good access to the Mediterranean, the South Atlantic, the Arabian Sea, and the Indian Ocean, etc. Putin had to have Sevastopol to keep up the pretense that Russia is a superpower.
While Ukraine had a Russian-friendly government and would let Russia use Sevastopol, that was fine. When Ukraine turned toward Western Europe and the US and flirted with NATO membership, it wasn't, so Putin invaded Crimea to secure Sevastopol. (Yes, a majority of the Crimean population is Russophone, and many identify as ethnically Russian. That was a good excuse and made the invasion easier.)
But Crimea is a big honking peninsula attached to the mainland by an isthmus that's way over in Ukraine. Russia built a bridge across the strait, but everyone knew it was a soft target, and indeed Ukraine blew a chunk out of it when the war started. Crimea isn't self-sufficient. Fresh water is very dependent on rainfall, and arable land isn't very productive. So Russia needs to be able to supply Sevastopol and the rest of the peninsula.
Putin was in a bad place, and attempting to annex the eastern half of Ukraine was a possible out. If Russia can hold the breakaway provinces (the self-styled DPR and LPR), by annexing them or by turning them into puppet states, it has the land bridge to Crimea and a buffer for it.
(None of this is meant to excuse Russia's actions, just explain why Putin saw this as existentially necessary for Russia's geopoltical status.)
Even better from Putin's point of view, of course, would have been to change the regime in Ukraine back to a Russian-aligned one. Putin greatly overestimated his capabilities and underestimated Ukrainian resistance and support from the West (tepid though that has been) and overstepped badly. What's worse is that the war has become a domestic dilemma for him: he's convinced many Russians that the war is necessary and must be won, but at the same time they're growing weary of its costs. And what's much worse is that the war persuaded Sweden and in particular Finland to join NATO, even under special terms, which is extremely bad news for Russia's naval bases in the Baltic and Arctic, and for St Petersburg and other targets in the area. Finland's military is nothing to sneeze at and they'd be capable of very swift and hugely damaging strikes against Russia in the northwest.
Putin's invasion of Ukraine is one of the most-predictable steps he's taken, deplorable as it is. And it backfired, and now it's all a big mess.