He won last time because the rats underestimated how much cheating they had to do.
Recall on election night that the 'counts' stopped around 8:30 pm CT for about 3 hours. During that time, the media were helping the Dems look for votes.
I strongly believe they found so many more votes for Trump that, if they cheated much more, too many precincts would have resulted in 120-130% votes -- more votes than actual voters.
A few precincts could be sneaked by, but it would have taken too many to push Clinton over the the line, thus showing overt voter fraud. They finally had to call it for Trump.