The hardest part about figuring out you're autistic is just the fact that so many of the symptoms are things that are perfectly normal, but you experience it to either an abnormally high or low degree. And you really only have your own experiences to go off of, so when you find out that one of your experiences is a symptom of autism, it's like "wait, you mean to tell me that's not normal?"
And that first discovery starts down the rabbit hole and before you know it, your entire life is flipped upside down and you spend months re-evaluation your entire life and putting the pieces together.