The idea for the invasion didn't start as soon as Biden was elected.
Regardless, of the date of Putin started lining up on the border. He was posturing. It is very highly unlikely to have invaded at all. If he had to deal with much stronger US leadership. And I am not the only one to say that. Putin knows we see everything his military does. With a number of assets and sources. If nothing else just orbital.
What do you think should be done now?
It has been said many times by many at a much higher pay grade than mine[was].
Biden drug his feet sending everything Ukraine would have needed to make Putin's little war never happen. Or at least him to think twice. It took months for Russia to get their forces to the border. We/NATO, etc. saw all that movement to the border. And Putin knew it.
Putin is no tactician or strategist and seems nor are most/ many of his senior officers. As well as his intel about Ukraine's ability to resist was faulty. Putin's move was to intimidate. And thought he would have repeat what he did in the Crimea in 2014. While Obama and Biden were in the WH. They rolled thru secured Crimea with little resistance.
Again, he was lining up on the border which took months. He was prepared to intimidate or roll into Ukraine again. Last time he did that Biden was VP. Now he was POTUS. Putin neither respected or feared him. Or Obama …
Once Putin saw how poorly Biden and his admin handled the situation in A'stan. He knew Biden, Blinken, etc. didn't listen to his Military and Intel assets. The plan was poor at best. And was proven out as so. Putin saw Biden was risk adverse and feared escalation. Putin then decided he would cross/attack into Ukraine.
Biden, and NATO would have followed the USA's lead, and rush more military aid/assets to Ukraine. Much sooner, which may have deterred Putin's invasion. And if not it would have given Ukraine more and better assets sooner. To do much more damage to the Russian Army much sooner. As it was, they did pretty damn good anyway.
Biden thought his civilian planned A'stan withdrawal was a success. No one who knows anything about that type of operation thought it could br considered a success. As it wasn't.
They thought they could just talk their out of it. Stop the invasion as they thought their A'stan debacle was successful.
They were very wrong. The Biden admin kept thinking they could just talk to Vlad, like they did with the Taliban. And were trying to do with Iran.
They all saw the weakness in the US leadership. They took advantage of it. Putin saw Biden did not think to rush equipment to Ukraine, as the US did to Israel during the '73 Arab-Israeli War. The word was the Russian invasion would be over in 3 days. Both Biden and Putin wrong.
Biden's risk aversion and fear of escalation was because the Admin feared/was concerned about Putin using his nuke. Even if only Tactical nukes. And Putin kept rattling the nuclear saber.
The Biden admin had other priorities than defense and NATO. It was all about woke progressive, DEI/CRT/1619, LGBTQ, Climate Change/Going Green, etc., etc. Putin saw that … he saw Biden's priorities wouldn't really interfere with his invasion.