The problem with Trump has always been his highly personal view of the presidency, wherein institutions, constitutional principles and sheer propriety take a backseat to the felt needs of his ego.
At times in his presidency, this failing has been made to serve worthy ends, e.g. stoking economic growth and confirming record numbers of conservative judges as bragging points.
Since the election, though, this tendency has been particularly stark and unredeemed. His personal inability to accept the sting of defeat has led him, shamefully, to wage war on a legitimate election.
If he were to somehow succeed in his goal of overturning the result, he would subvert American democracy and irreparably harm our governing institutions, while stoking a constitutional crisis of a magnitude we have only experienced rarely in our history.