Maybe they want him to play Robin to Jeb’s Batman. Or vice versa.
Rubio can’t be on the same ticket with Jeb since they both reside in Florida and the electors can vote for no more than one person from their own state. If the Republican ticket won narrowly, taking Florida, then the Florida electors would have to vote for someone other than the VP nominee, throwing the election for VP into the Senate where each Senator would have one vote. So if the Republicans had retained control of the Senate it might work but it is a risky way to go about it.
Rubio can’t be on the same ticket with Jeb since they both reside in Florida and the electors can vote for no more than one person from their own state. If the Republican ticket won narrowly, taking Florida, then the Florida electors would have to vote for someone other than the VP nominee, throwing the election for VP into the Senate where each Senator would have one vote. So if the Republicans had retained control of the Senate it might work but it is a risky way to go about it.