I think it fits him, story wise it makes perfect sense because of his past given how it would prove sora right, that not only emotions make you a better person, but they also make you stronger and a better leader
Does he need it? Definitely not, his fire based abilities are basically only restricted by the plot
Was he forshadowed to have it? Not really
He does have the "strongest ability in the world" which is turning his opponents into allies like he did with the g5, Duval's crew, gin etc....
But he was never explicitly shown to have it, but there were a few instances were he was extremely intimidating like when he scared nami by glaring at her when he faked being a traitor during wci
The lack of forshadowing is the only counter argument, but his character fits the criteria for CoC perfectly, he's a natural born leader with a strong will
And btw, I see a lot of people trying to argue that his dream contradicts what it means to be a conqueror
Whitebeard's dream was to find a family
Don chinjao wanted a treasure
Yamato just wants to set sail with luffy
They all don't have a "kingly ambition" if we focus only on their dreams