Obama was saying this back in 2016:

Obama declares Ukraine to be not a core American interest and that he is reluctant to intervene in the country, because Russia will always be able to maintain escalatory dominance there. “The fact is that Ukraine, which is a non-NATO country, is going to be vulnerable to military domination by Russia no matter what we do.”—President Obama

April 2022

For me, I would say around 2020 and knowing the US was responsible for blowing up the pipelines the around summer 2021, considering the news at that time I could already tell. Not in detail, but enough to know it a high likelyhood, with doubts in between.