I think what he's getting at is if voter fraud happens in one place, and massive, in a highly densly populated area, will get offset by the rest of the nation with an electoral system. It's very hard to do fraud everywhere, and if one wanted to do that, their best bet is in those highly populated densely packed areas.
For example California. This is odd and highly suspect. But doesn't prove fraud.
"Clinton won the state with 61.73% of the vote and a 30.11% margin, both the highest since
Franklin D. Roosevelt's 66.95% vote share and 35.25% margin in
1936. This was also the first time
Orange County voted Democratic since
1936, when Franklin D. Roosevelt swept every single county in the state."