No one is a telepath. We can't know for certain what Putin was going to do. Not even his own military commanders and troops it seems.
You're rewriting the narrative. The US/UK had exceptional intelligence, and threatened and - in the US - already had the sanctions pre-approved in the Congress/Senate. It had aligned the banking and financial institutions to conduct a biggest economic sanction in history before the invasion, and got global agreement to those actions. There were stipulations - wait until they cross a line - but the work done and since are quite remarkable. This on top of getting arms into Ukraine ahead of time in huge numbers, which has paid off dividends.
Even in this same thread we had people saying Ukraine was toast, days at best, and it was inevitable. But it hasn't been, in part to the prep that was done. Could they have been proactive or more aggressive in language - I suppose - but that could have peeled some support away or given Russia a stronger hand (especially with China or India) if the West had proactively ripped the banking system out from under Russia without them taking the first shot. It would have for sure undermined trust of those systems for all nations, which would've had huge long term consequences.
So other than playing a what if game or wanting to blame people in the west for Putin's individual crazy behavior, Ukraine and the west have about a good of hand as they could have expected or gotten.