Please forgive this general theory question.

Of course I understand that the conventional wisdom recommends isolating one opponent when you have a big pair. However, Angel Largay recommends letting a big field see the flop with you with TT-QQ. The math bears this out:

If you have JJ and just one opponent, and both of you put in $100 to see a flop, your equity against a random holding is 78%. 78% of 200 is $156, so that is your equity.
Your price is $100.
So your EV = 156-100 = $56.

Now, say you have let 8 opponents with random holdings see the flop with you. Here, your equity is 20% of 900 = $180
Your price, again, is $100.
Therefore, your EV is 180-100 = $80

So your EV is $24 greater if you let 8 people see the flop with you versus when you let only 1 see it with you.

This got me thinking: surely this is true of AA as well. In fact, the math shows that it is:

AA versus 1 random opponent
Equity: 85% of 200 = $170
Price: $100
EV: 170-100=$70

AA versus 8 random opponents
Equity: 34% of $900=$306
Price: $100
EV: 306-100=$206

So you gain 206-70=$146 in equity by letting 8 people see the flop with you.

Of course, this assumes that 8 people will pay $100 to see a flop. But doesn't this suggest we should try to keep as many people in the pot as possible when we have AA? And that if we raise, it should be a small, pot-building raise that will encourage people to stay in, rather than a big raise designed to isolate one opponent?

The next question is, what do we do when we flop on overpair and 8 other people see the flop with us? Bet out and fold to resistance? Check-call until we feel we are beat? Check-fold unless we hit a set?

If I am missing something, please tell me what it is.

If you believe it is, in fact, better to isolate one opponent, please explain to me why you think so.

Your reverse implied odds suck multiway with AA postflop, since hands like 22 and 87s will generally be able to play their hands with a good idea of where they stand, but AA will get in many situations where they fold to draws, or call against sets/2pair type hands.

answered your own question methinks.

Your EV calcs exclude postflop action. You do want a multiway pot if you are getting it all in pre flop, but if you have cash behind it changes your overall ev for the hand.

It almost like although EV is higher in multiway it is much harder to crystallise that EV versus more players post flop.

As has been said already, your initial calculation lacks an analysis of implied odds and reverse implied odds. It is better to see the flop heads up or three way simply because you can attach a reasonable range of hands to your opponent(s) and stack off less often during the times you're beat.