Quite frankly, Jason was already very impressed by Adele's commitment to her dreams and even identified with her quite a bit as they both had dreams that they were willing to do almost anything for.
Not to mention that he liked her work ethic which already did a lot to display how far she would go to ensure his benefits if he hired her as his agent.
Also, he didn't even have anybody in mind for an agent in the first place and the girl worked for the company that Jorge Mendes, the super agent who worked for Cristiano Ronaldo created, so he was quite literally already sold on hiring her.
There was even the added benefit that he was to be her first client thus she would not have that aggressiveness and hard-headedness that other agents who already had clients would have that would make them sometimes ignore the client's concerns thinking themselves to know best.