I don't think this was avoidable, Putler has been building and planning towards this for nearly 10 years.
And I bet he even counted on his toyboy and bitch Donald to be the president of US at this point. If you think Biden's speech is senile rambling, just check out what Trump is tweeting.
US and EU should be doing more to sanction Russia I agree, but I think Putler has to be surprised how united EU and US seem to be. And they wouldn't be if Trump was the president.
You are willfully ignoring the fact that Putin has already sent Russian troops into the Ukraine to annex the Crimea... during an Obama/Biden administration. So, 2 incursions into the Ukraine, both while Biden was in the White House (first as VP, now as President). But sure, Putin must have been banking on not having Biden to walk all over a second time.