Bolton all but begged the Democrats to subpoena him. As I recall, he was trying to get himself added to the trial of that other guy to get Congress the right to question people under a White House order to not talk.
On the other hand, Pelosi and Schiff kneecapped themselves about as much as humanly possible. And, realistically, the only reason for them to have done so was because they thought it was more useful to use the event as a fundraising venture rather than make any real attempt at prosecuting the case.
Unless you believe that Schiff was the world’s worst prosecutor to ever walk the Earth and somehow Pelosi never noticed that his head was full of sand then, until you’re ready to throw them two under the bus, Bolton is still in the clear so far as blame goes.