I get that, but it's a crazy move IMHO. Go where, at best, you're sharing targets with 4-5 other WR likely better than you or stay where you will be featured in an O that will likely fill the air with balls. For a few dollars. All the while leaving a school that has put about 10 WR's in the League since 2000.
My guess is the pitch goes like the following:
1) Much higher NIL money than at Tech (though personally I question how much someone like him is getting)
2) Legitimate chance to win a title in 2 years versus legitimate chance to make a low tier bowl
3) Play in front of a mostly packed house every game
4) U[sic]GA has a lot more experience putting players in the NFL -- they've had 130 players drafted over the past two decades versus only 39 for us
5) The talent level at U[sic]GA is much higher, which will push McCollum to develop more and prepare him better for the NFL
1, 2, and 3 are immediate, indisputable personal benefits and it's easy to see why they would be a big deal. I know a lot of people say a lot of these players are only interested in making the NFL, but I think most of them really would love a shot at winning the title. You don't see many players opting out of the playoffs.
The big question is whether #4 and #5 combined with playing a middling role on a top team are more valuable than playing a starring role on a middling team for a second year. I don't really know enough about how the NFL evaluates prospects to say, but I am sure that U[sic]GA will be trying to make the case that they give him the better shot at a high NFL draft pick.
Regarding going to your arch rival, I think that matters a lot less when the rivalry has been so one sided for three years and you were playing in front of mostly empty stands for a coach who didn't seem to care much about Tech traditions. My fervent hope is it will be different under Key.