EPs are considered mobilizers because they very often
START things. That is, in a way, their job. They get things moving, get people moving, get ideas moving, even get themselves moving. Getting something moving doesn't mean that that thing has to stay in motion. You get it moving and then let it do its thing, then it winds down, and the EP steps in and gets it moving again.
This is why EPs are good for bouncing around from task to task, getting things going into the direction intended, but then leaving it to others to keep it going there, and the IPs to alter the course AFTER things have been set into motion.
This is how EPs and IPs can work together well.
The EP gets things moving, and then steps back...
The IP steps in, watches the movement (not keeping it moving themselves) and then lets the EP know if changes need to be made....
Then the EP steps back in, pushes the movement into a new direction, steps back again, and awaits for the IP input...
Repeat as needed....