There is also this boxing politics that's why we seldom see mega-fights because of this ABC title belts. Let's stick to the subject though, even though Crawford is the favourite, we are going to see a exciting fight for sure as Kell Brook won't back down from any challenges, like you said, he took his chances against GGG.
The politics in boxing is what restrict two great fighters to go for each other, take the case of Fury and Joshua and the should be done fight of Wilder against Joshua, it did not materialize because of the too many politics and the shares of the money on who should get the big slice, promoters and the organizations wants to push the potential of a big fight to the limit, this is to generate more money and interest.