Boiled down, the reasons are:
1) he’s polling decently (not great),
2) he’s apparently preparing to run, and
3) he’s got non-political experience.
#1 is primarily a factor of name recognition, as are all early presidential polls.
#2 pertains to anyone who runs.
#3 has really not got anyone anywhere since Ike’s quite different, military experience after WWII.
#15 He wants to insure the field is dilute enough that no Conservative can win.