Look. I believe in the multiverse. And in the multiverse, there are an infinite number of things that could happen. And you make choices that affect what happens. And you have to decide on whether certain things are good choices or bad choices. And you look back to those choices, and say whether they're good or bad. And you wonder, "what if hadn't made that choice?" A world where you had made a different choice is Alternate History. Simple as that. And if you think alternate history is pointless, you can't look back on whether that was a good choice or not.
You can look the complicated details on whether or not it would happen, and make that an excuse for saying that Alternate History is pointless.
But really, if you can't look to the past to see the choices you made in life.........you can still be a good person but you're going without a real good perspective.