Social media didn't exist then, hell the internet didn't exist then. It is hard it imagine how little information there was about this sort of thing.

When Halloween III came out all we had to go on was the poster and it was seen by basically no one in its cinema run.. It was mainly shown in drive-ins as most cinemas didn't bother screening 18+ rated movies.

So, no, no one really knew or cared who Myers was or that he was not in it.

The Halloween series and horror in general did not take off until home video did and that was still in its infancy.

It was probably at least 5 years after its release that I watched it.

I read somewhere they were trying to turn the franchise into an anthology series of movies but it ended up bombing at the box office.

But hey, we got that great Silver Shamrock theme out of it so it can’t be all bad!

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.

I wasn't around at the time, but I hope you find the answers you're looking for.