Idea
The Pun Tyrant
Well, the whole concept just bundles together a lot of things that are very useful, if often just treated as shortcuts, from a writing perspective. Being an orphan has the whole drama of dead parents and associations with a bad or at least impoverished environment to grow up in, there can be ties to the plot via why the parents died, it can be motivation, also who those parents are may be tied to the plot or worldbuilding or serve as a twist or justify something about the protagonist, etc.... Plus being an orphan will also often let the hero be an underdog at the start or excuse why they haven't been using their talent or maybe put them in the care of people who mistreat them because they don't really know them etc...
On the discovering they have powers side you have this idea of "wow, if this random orphan secretly had powers wouldn't it be awesome if you did too?", plus powerful gifts in of themselves can be huge plot and character drivers or be at the center of the action, mystery or generally fantastical/epic aspects of the story.
A mentor figure can have plot ties, is more wise and experienced but ultimately intended to be surpassed, thus serving as a benchmark while also helping the protagonist (and the audience) to get introduced to the worldbuilding, plot etc... They can serve as a unique close relationship, often cashed in on upon the mentor's death, they can help progress the protagonist to the point of it being a little more believable that they can do the kinds of feats they can later....
I could go on, but I think my point is made. Tropes are often tropes for a reason, and while some just use them just because, there's a lot to unpack about their potential, a lot of useful things they carry.
As a sidenote, I don't think I would characterize you average mentor character as manipulative, much less in this trope sequence. Persuasive or a little forceful, sure, but I think a mentor that is manipulative is its own thing that can or not coexist with the whole sequence of the orphan destined for greatness tropes.
On the discovering they have powers side you have this idea of "wow, if this random orphan secretly had powers wouldn't it be awesome if you did too?", plus powerful gifts in of themselves can be huge plot and character drivers or be at the center of the action, mystery or generally fantastical/epic aspects of the story.
A mentor figure can have plot ties, is more wise and experienced but ultimately intended to be surpassed, thus serving as a benchmark while also helping the protagonist (and the audience) to get introduced to the worldbuilding, plot etc... They can serve as a unique close relationship, often cashed in on upon the mentor's death, they can help progress the protagonist to the point of it being a little more believable that they can do the kinds of feats they can later....
I could go on, but I think my point is made. Tropes are often tropes for a reason, and while some just use them just because, there's a lot to unpack about their potential, a lot of useful things they carry.
As a sidenote, I don't think I would characterize you average mentor character as manipulative, much less in this trope sequence. Persuasive or a little forceful, sure, but I think a mentor that is manipulative is its own thing that can or not coexist with the whole sequence of the orphan destined for greatness tropes.