Yonkou system was in place to prevent anyone getting to laugh tale.
Fall of two yonkous with RPG broke that balance.
Luffy, Kidd and law with RPGs got the edge.
So it's common sense that other big pirates will come after them to get the hands over RPG.
They are pirates and so I am actually fine with the concept of BB and Shanks stealing RPG when they are getting the opportunity to do so.
I mean what else you expect from pirates lol
And, there path has to convege since everyone is targeting to reach laugh tale.
So, it's actually great idea.
Infact, I remember that many people had issues that why SN members aren't competing with each other or fighting amongst themselves as they are competitors.
And, now when oda is showing pirates fighting for RPG - it's also an issue lmao