I definitely think Trump, and his many supporters share a good portion of the blame for what has happened in Ukraine. Here's a good piece I ran across which gets into the ties between Trump and Putin.

It’s time to confront the Trump-Putin network
Rebecca Solnit
Wed 2 Mar 2022 11.22 GMT
A stunning number of Trump’s closest associates had deep ties to the Kremlin. The significance of this cannot be overstated
[theguardian.com]

"...Of course the most striking role of the Russian government in the 2016 US election was its many, many ties with the Trump campaign, including with Trump himself, who spent the campaign and the four years of his presidency groveling before Putin, denying the reality of Russian interference, and changing first the Republican platform and then US policy to serve Putin’s agendas. This included cutting support for Ukraine against Russia out of the Republican platform when he won the primary, considerable animosity toward Nato, and ultimately trying to blackmail Ukrainian President Volodymyr Zelenskiy in 2019 by withholding military aid while demanding he offer confirmation of a Russian conspiracy theory blaming Ukraine rather than Russia for 2016 election interference.

"A stunning number of Trump’s closest associates had deep ties to the Russian government. ...."

"....What’s striking in retrospect is that all of this was made possible by corruption and amorality inside the United States. It was Silicon Valley’s mercenary amorality that created weapons and vulnerabilities and sat by pocketing the profit as they were exploited to destructive ends. It was corrupt Americans – from Manafort to Trump himself – that gave Putin his influence. It was international players such as WikiLeaks and Cambridge Analytica that helped. It was corruption of media outlets such as Fox News that continued – in Tucker Carlson’s case until last week’s invasion of Ukraine caught up with him – to defend Putin and spread disinformation...."