Two groups are to blame.
The GOP for protecting Trump when he was down and they could have parted with him.
The DoJ (and Biden) for thinking they will win favor with the republi'cans' if they bend over backwards to try and appear unbiased and impartial, and thus letting Trump skate as long as they did.
Garland in particular is so over concerned about not looking political that he would have NEVER acted on Trump had Trump not declared his run. The irony being Trump declared so early thinking that 'of course Garland and the DoJ must be about to act' and that is the only reason Jack Smith might get his trial in. Had Trump just waited to normal time to declare, and Biden put Smith in then, he would have had no chance to get a trial before the election.
Garland just does not learn. He left Durham in place investigating the 'crime of the century' thinking it would get him and the DoJ good will, with Magats, and it did not. He and Biden left Weiss in place, even though the norm is for the new POTUS to replace him, thinking it would get them good will with Magats, and it did not.
As soon as Garland took office he should have empowered a Special Prosecutor to look into all crimes on Jan6th and investigate Trumps role. He, like the rest of us, watched a sitting POTUS try to stay in power illegally and who inspired a violent insurrection. NO one would call it hasty or political, at that point, when both the House and GOP leadership were blaming Trump and saying the DoJ and courts had a role in addressing what Trump did.
History will not see Garland well IMO. he is weak and feckless and second guesses himself based on looking over his shoulder and seeing MAGA shadows he wants to like him.