The Infinity War trailer showed us the Civil War fracture was still on. Spider-Man, Tony Stark, Dr. Strange, Wong, and Bruce Banner are shown in New York fighting a major threat while the non-participants, Thor and The GotGs are out in space. Presumably, at the same time, a completely different set of Avengers led by Cap, BP, and Bucky are defending Wakanda from an invasion. War Machine couldn’t be with Tony because he’s busy with Cap. And they’re joined by... Hulk?
No other characters crossovers in those scenes. You’d think they’d have Iron Man in the major battle in Wakanda. Or Dr. strange, or Spider-Man. But they aren’t. Because they’re busy. In New York. what about the flip side? Cap is only shown in Wakanda and fighting Proxima Midnight, and BP talking about him. Widow is only shown in Wakanda, and ... stabbing Proxima. Falcon, Winter Soldier, BP? ONLY shown in Wakanda. The two teams are completely separate as far as we know. We see lots of Iron Man, but even with trouble rising its only Bruce Banner at Tony’s side.
So Hulk is with Cap at the same time Banner is with Tony? Boom.