Firstly, because we had a valid pretext for war (Taliban et al). But very important too is the fact that wars are profitable. And not from a resource standpoint

Firstly, because we had a valid pretext for war (Taliban et al). But very important too is the fact that wars are profitable. And not from a resource standpoint; war production itself (e.g. weapons manufacturers, engineering firms to rebuild, etc) is highly lucrative and there certainly were agents lobbying on behalf of those companies, and pivoting themselves to be in a position to provide services "in the event of a conflict". That resources were actually discovered during occupation is just icing on the cake.