I was too young to have watched Halloween at this point but I read the sci-fi/fantasy film magazines and there may have been a few raised eyebrows but it wasn't really a big deal. If they'd done it with two, no-one would mentioned it.

This was still very early days for movie franchises and there weren't really any "rules" or expectations. I think people were surprised Halloween got a sequel and not many really thought there was much mileage in even more films about Mike Myers. Ten films later and some people would still stick with that opinion.