The Uniparty forced Trump to accept Pence as his running mate or else the Republican Party would pull Trump's nomination as they had the power to do, even though Trump was clearly the popular pick.
The plan, as has now been evidenced and is called the Coup, was to oust Trump after he won and replace him with Pence.
The PTB knew that they could control Pence because, it is rumored, they had some dirt on him which he would not want exposed.
Interesting that the envelopes were given to the wives. One could assume some secret dalliances of various sorts?