repeating a few points here but:
1) Cornhole is simple. Anyone can play it
2) Cornhole is quick and easy to set up
3) Cornhole is quick and easy to play
4) Cornhole is fairly portable. It can go to all social gatherings
5) Cornhole can be played outside, during BBQs, or on the beach, etc
6) Cornhole is inexpensive
My neighbors across the street spent half their 4th playing it on their front yard with beers in hand. Any outdoor social gathering I go to has some cornhole set up.
Cornhole is not a good comparison with pool. Pool is expensive: you need a pool table. Pool cannot be played outside. It is not portable. It is not quick and easy to play or set up. Pool is much more complex.
I think pool is a much better game/sport than cornhole. I play cornhole maybe once a year, and mostly just because I get myself in position where I feel socially obligated, whereas I own my own pool table on which I play almost daily. That all said, I can 100% understand why cornhole has become popular (all the reasons listed). Anything people can do casually and easily and socially while drunk has a real chance to be popular.
The real comparison isn't cornhole and pool. It's cornhole and...I dunno, horsehoes, as previously mentioned? And the difference is that horseshoes is your great-grandfather's game, while cornhole is new? Guessing, of course, but only time will tell if it has staying power or if it's just more of a fad.