Although it's hard to predict primary politics this far out, DeSantis:
-is a Governor. Governors usually perform better than Senators.
-Is from a swing state, and a huge one at that.
-Has notable nonwhite support.
-is the least-scary of the 3 to establishment and moderate Rs, while still remaining popular among Trump supporters.
The last two points are important with Texas and Georgia as a battleground, and the GOP cannot afford to lose FL and NC going forward, as I believe Arizona will lean blue from 2024 onwards.
Although I like Hawley and (somewhat less so) Cotton, their appeal seems more niche.
DeSantis has to win Reelection first in 2022 before we can talk about him even thinking about running for President.
DeSantis could be the George Allen of 2008. Allen was being talked up running for POTUS in 2008 but then he lost to Jim Webb in 2006 and was damaged goods after that.
Hawleys Senate Seat would be up in MO in 2024. I'm not sure if Missouri has a Law where he can run simultanously for Senate & Senate. Some States have it, some States have not.
Cotton probably has the inside track here of those 3 since he easily gets reelected this year and therefore his Seat would not be up until 2026.