I was a pollworker in California this past election. Why do you think mail balloting is "a lot of fraud" compared to what happens in a polling place? At the end

I was a pollworker in California this past election. Why do you think mail balloting is "a lot of fraud" compared to what happens in a polling place? At the end of the day it's still a signature on a sheet of paper combined with a check before counting that nobody was recorded to have submitted more than one ballot.