S.Lazzaro di Savena
I would think that leadership maxes out at 25.
What makes you think that leadership is max 25?
The last number in the Leadership Track. And the fact that there's room for at least an additional line under it. And the knowledge that printing another line of number does not add costs to that card.
So there's room for it, no costs for it, but the Leadership track ends at 25.
Is there something in the rules that leads you to this conclusion?
No. It's a "clue" from the components.
The rulebook is not a bright example of completness and clearity, I've seen a lot of other rulebooks saying something like "while the score track on the board ends to 100, you can continue counting score and the game don't end when you reach 100". It is something required when you have compromises between components and mechanics.
While I'd say that Leadership max is 25, i recon that the rules did'nt mention it. So I'd like a official answer.