Tim has a lot of experience in the whole adventurer thing, having started when he was ten and getting his parents killed. After being taken in by Bruce Wayne, a top adventurer in the 'Bats Sect', he thought that he had his life pathed out with him; he'd join the sect that his new father led and then either get a wife and have biological children or adopt a haggle of misfits.
However, that path that he had thought that he wanted had changed when he met a prodigy around his age. He was also a prodigy in terms of magic and the bo staff, but the prodigy that he had heard of was most likely even better than what he has done in his short life.
The prodigy that he has heard of has four affinities, four! He only had two affinities; light and water, which were a pretty good combination, but the prodigy that he has heard of has better control of their elements ever since they were a child, and that's crazy because most people found their affinities when they became ten to twelve years old!
On top of that, the prodigy has destroyed cults, tamed dragons, killed demons, and did everything that only those in fairy tales could do. That is why he came to idolize the prodigy that he had heard so much of.
So when he was choosing his sect, he chose his idol's; the 'Elemental Sect' with wishes that he'll be as great as his idol. When the leader had tested him, the leader had mentioned that he has great potential, and that he'd be trained by one of the greatest.
When he was brought to the room which had his mentor in it, he immediately recognized the mentor as his idol; the prodigy of the sect.