why?
just upon googling "voat":

top 3 sublinks are jailbait research, fat people hate, and a sub LITERALLY called "mondays". also one of those links is literally for voaters to spy on reddit, further cementing the idea that voat can't exist as its own community at all, but only as a foil to reddit where nothing interesting happens.
voat is also super on the right politics wise. at least reddit sort of has a political spectrum going on (with The_Donald and related subreddits being on the right, and most of the rest of reddit being center-left) though I'd argue that reddit is a lot less liberal than people think
reddit is really prone to circlejerking and echo chambers and is kind of garbage because of that. if you sub to non-defaults with strict moderation they tend to be pretty quality though
it is also just different than twitter or facebook - you can't have conversations in the same way on reddit, its more about content then it is about people. so something else would need to fill that niche