Chalk Law's backstory, ties to Doflamingo, and his prominence at this juncture as a whole up to his popularity. Oda thought Kid would've played a bigger role than he did but Law probably took that spot instead. We probably won't see anything resembling Kid's motivation until after Wano, if at all. Hell, we still don't know why he raided Totto Land. If anything it'll either end up in the SBS, a data book, or a light novel a la Ace's Story or Novel Law.
On that note, I'm curious as to what the hell the Rocky Port Incident was. All we have is that Koby was there and saved a lot of civilians, that Law was behind it, and that it most likely ended up with him taking the hearts of 100 pirates and handing it over to the Navy (I pieced this together from the fact that the first mention of it was at the Seven Warlord discussion in Chapter 700 and that the whole heart thing is what got him the position).