If you really did see a few people expressing genuine happiness that Charlie Kirk died and you’re not just being a moron, I highly doubt that it was "the vast majority of the democratic voter base." You likely extrapolated the comments of a few shameless individuals to all less extreme comments that didn’t provide unqualified support for Charlie Kirk in the aftermath of his death, and that’s if I’m being charitable. It’s why no one takes these accusations based on anecdotal evidence seriously.
3995 likes isn’t a lot by any means, which isn’t particularly surprising since that is Charlie’s page and anyone who isn’t an alt-right conservative would likely have to go actively searching for it. I am absolutely sympathetic to some of those comments, but sure, now demonstrate that it was the "vast majority of the democratic voter base."