What I remember reading about the decision to launch the A380 is that at the time where the B747 was in hot demand, Boeing had no competitor for the jumbo jet, and used that as a point of pressure on airlines: you’d better order Boeing for smaller jets if you want a nice price and place in the queue for the B747. So that likely weighted on the decision to launch the A380. But I remember at that time, it wasn’t an obvious decision to make (not the least because airports had to redesign their gates to accomodate such a large plane).