Because the Electoral College has worked out so well for us here in the US. /s
As someone who's actual real life votes have been watered down all my life, I really don't want to apply that logic elsewhere.
Why not just make new account's votes only count for 3/5 of a vote and send those in aggregate? /s
The real solution is to be aware of unmoderated / malicious instances. Vote manipulation is something I actively watch for, and I didn't even see this campaign because I'd already defederated from both of the identified instances as they were already frequent sources of spam. After looking into them, neither seemed actively moderated and both had open signups. Doesn't take a rocket scientist to figure out how that's going to end up.