I thought, in order to be a deus ex machina, it had to come from nowhere. Like a dragon chariot from a God. Why not? What do you mean I never said such a thing existed?

Whereas the ending of Raiders is explicitly telegraphed and foreshadowed from the first image we have of the ark. You see the light beams shooting out and people cowering from it. It's clear that something's in there, and it's not friendly. It's the gun in the first act. It had to go off in the end.