Think of the Constitutional process in terms of an invasion by a rogue division of Mounties marching on Detroit City.
Assume the President, taking delivery of his new limousine, has been taken captive.
You read the Constitution in that light and it all makes a lot of sense, particularly all the parts about Congress.
Again, the context is the Constitution, not the War Powers Act, and not the spineless weasels we've had as Congresscritters for the last 189 years.