Did anyone aside from terminally online edgelords cheer for that though? I don't know that I saw anyone serious celebrating his death, certainly no members of congress. I do find it odd that the reaction from twitter and reddit bottom feeders (and the likes) stirred you so much. For me politicians actual vile comments and complete indifference to the assassination (or attempts) of state representatives and their families is much more disturbing than what people on some Sopranos meme subreddit had to say about Kirk - but perhaps the Hortman's were those 'others' you mentioned?
It's the volume that I found disturbing. There were Twitter posts celebrating or mocking Kirk's death, using images of his murder, with nearly 1MM likes, hours after he was killed. At the time, it was being reported his wife and toddler daughter had been in the audience (thankfully later revealed to not be true).
I haven't seen anything comparable for Hortman but if I had, I agree I would find those incredibly disturbing too.