Why not? If he's going to protect his kids from harm, he better be a lot more athletic. Besides, it's one of those things we have come to accept in the Pokémon World. Just like how some superheroes don't really need an origin story to understand why they are doing it.
It made sense in the beginning since Clemont wanted to gain confidence/become brave/be a heroe/etc, that he would eventually help out Blaziken Mask, realize it is his father, and then one day succeed him. But...it just ended up with Meyer being a superhero.
Also, as I wrote in Anime Polls. The PTSD arc of Goodra should have gone to Greninja. Maybe Ash jumping off a skyscraper to save Pikachu reminded Froakie of something that he saw. The pain-sharing aspect of their synchro could be Ash feeling Greninja's mental scars. Could have been actually compelling, instead of Ash conveniently owning the next incarnation of the Chosen Amphibious One of PokeFrance (though it randomly has a ninja village in the middle of it). Greninja becoming the savior and staying as Kalos protector would have been a fitting end to this arc.