How much money does meta even make from political ads? Why would they even want to deal with this?
My old coworkers had a story about this. Back in 2012 the romney campaign was spending so much money on facebook ads they couldn't be served fast enough. Coworker was told to turn off the "don't show me ads like this again" functionality for Romney so they could get more views. I don't have numbers, but it's hard to fathom how difficult it would be to literally run out of people to advertise to at facebooks scale.
Probably because they were doing hyperspecific targeting, not because FB literally didn't have any more users to serve ads.
I doubt political ads are a major part of the mix - for one, there is little evidence that they are all that effective compared to TV ads.