I suppose Indy Noir (a darker vision for Indy IV that some of us used to articulate) was before your time here...
But at any rate, spies are pretty darned pulpy, and if you're going to do post-war intrigue, Carol Reed-style shots are pretty natural, and the sort of thing that would probably attract Spielberg's attention anyhow. (Think the Lean homages in the India trek, or portions of Raiders, or the John Ford-style vistas in the opening of Last Crusade, or the Busby Berkeley number in Shanghai. The films are exercises in homage - that's most of the fun for Spielberg and Lucas, I think. So I wouldn't put it past them. If pulp was globetrotters and mobsters in the 30s, and aliens, Commies, and the bomb in the 50s, then the 40s was the war and the coming cold war and shadowy agents hiding in every doorway. Street lamps shining on wet streets amidst the rubble of a bombed-out city...it's a natural, especially for a series that spent so much time dealing with the Nazis when they were looking for artifacts: then there's the aftermath.