Alex was interested in participating in the tournament.
No, he didn't have any interest in being a Hero. That was the last thing he wanted. To live under surveillance for the rest of his life was something he could never allow.
He was interested in the tournament because of other reasons. For example, it was a great place to test his physical strength and learn new techniques. Having more experience in close combat wouldn't do him any harm.
At the same time, he could learn in-depth about the abilities of the nine great tribes. That would help him defend against them in the future.
Besides that, he could also use the tournament in his favour. He could scout talented individuals to work for him. If he could find a dark horse among the contenders, that would allow him to expand his business even further.
With a strong warrior guarding the front gate, most problems would solve themselves. Alex doesn't need to solve all the problems himself.