Let's suppose that Obama's presidency is the reason Trump was elected. My wife thinks so. She thinks that Obama did not do enough for the working class, thereby setting the stage for a populist. If she and you are right, then Obama shares responsibility for Trump's rise due to incompetence.
It in no way follows that Obama is the primary villain. Trump, his followers and especially the grownup GOP in the Capitol are responsible for what is actually happening now. Obama does not encourage vile bigotry, Trump does and so do his Republican enablers.
If Chamberlain's appeasement led to the Holocaust, he is still not the evil behind the genocide. If Obama's presidency paved the way for Trump, he may share some blame, but we all know where the real evil is.
....and one of the reasons (the main one ?) why Obama was unable to achieve very much was that the GOP, from day one, was dedicated to ensuring that Obama got nothing done.