I don't know, 2016 had Benghazi and Killary, which is perfectly fair to someone that would campaign with Kissinger, but no couch fucking weirdos and hate speech so open even the centrists notice it.
They cooked that one up months before the campaigns even got underway. Hillary was always a terrible candidate I. this regar; that they had know she'd do a big run, and had literally decades to build oppo research and a smear campaign. I mean, it was obvious that she was a bad candidate in this regard as early as 2013.
Harris I think really did catch them off guard. Which is a bit surprising?
I don't think they're either really "on purpose" or "accidents". It's not calculated or truly random, it's just who these people naturally are. And it plays because unfortunately a lot of us Americans are idiots.