Can anyone explain the decision behind having Claremont using Wein and Cockrums newly created X-men?

So this has always confused me(please correct me if I’m wrong about anything). So in 1975 Len Wein and Dave Cockrum write Giant-Size X-men#1 creating a bunch of new X-men to lead a new team. But then Chris Claremont ends up being the one who writes the new series featuring the newly created X-Men.

Did all three of them know this was going to be the situation going into it? I would love any insight into this because the whole situation seems strange to me.