It's a money thing. Mercedes and Ferrari give teams discounts on their engines so they can have a seat for their academy drivers.I still think it's wild as hell that another team can control who another team picks for their driver, like Ferrari gets a seat for Alfa, but it's extra nuts when Merc has a drive with Lewis who is trying to champion diversity and his boss is outright stopping it.
You took quite a leap to frame this as Mercedes blocking diversity

How about looking at it as Toto doing Albon a favor by giving him a Merc junior seat, at a time when they have 2 drivers without a car with Formula E team shutting down? So if Horner really cares about him and in turn diversity, even though they couldn't give him one of their four seats, how about they release him?
You forgot Horner talking shyt how he would give Ocon a Toro Rosso seat if Mercedes released him? And Ocon eventually did have to be released to get a Renault seat.
They should've told him from the jump not to go for the fast lap before he put in two fastest sectors but they've been in shambles the whole race, the whole yearI also thought it was super funny that they came onto the radio to Bottas and tried to stern voice him into slowing down when they're kicking him to the curb next year......and this is a year after they tried to play hardball when negotiating with Lewis.

Not nearly as bad as Red Bull piting Perez out of a top 10 finish few races ago so he could take the fastest lap away from Lewis.