I think the question “why do my armpits sweat so much?” is a great question and I am happy that you asked it. It tells me that you are having a real problem and you are looking for a solution.
Did you know that I asked that same question for many years? I rarely ever asked this question to anybody else, but to myself thousands of times.
I always felt ashamed that my armpits sweat so much and always left huge, I mean huge, sweat marks behind. It took me years in finding out what clothes and in which colors I could wear to make the terrible sweat marks less visible.