Europe is that reliant on Russian gas. It's rather simple to not certify Nord Stream 2 since it's not operational thus not in use and relied on. Different story about Nord Stream 1. I think we are already seeing a shift in US O&G production (things seems to have gotten funny) to counteract the need for Russian gas but it'll take a while for anything substantial to come online (better to not rely on petrol at all...).
Honestly, I think most people were expecting Donbas to be at most what Putin wants, not wholesale regime change (I kind of don't buy the idea of going through all this to have an East and West Ukraine unless as a fall back plan). Ukraine probably would've given Donbas and others up after a struggle. This is probably why there wasn't much reaction to the official Russian "peacekeeping" force from earlier in the week (or even with Crimea back in 2014). Like it is very aggressive but have your fucking buffer state. Then of course, the full-blown invasion happened, which included Belarus involvement! Even the Russian troops in the separatist region of Moldova didn't run over (it's obvious why the Russian came over from Belarus, it's a stone throw to Kyiv).
Putin was seen a somewhat sane but after his speeches before the invasion and with the invasion, he's off his rockers. May the Ukrainians hold the Russians till they give up this fratricidal war. I think a lot of the Russians troops and civilians (the Russian anti-war protesters are brave as fuck) realize this is so pointless.