It's not just about Muslim countries having rules about drinking alcohol and nudity or any other rules, there are some rules in any country and all the visitors should respect these rules in Qatar, I saw many people say they can drink alcohol even in stadiums but they need to spend more money and buys more expensive tickets which is a bad side of the story when some people are allowed to break rules and some other people are not allowed.
It has nothing to do with Qatar being a Muslim country. If you have money, then you can do whatever you want in that country. Beer and other alcoholic drinks were permitted for some of the fans, who had top tier tickets, but two days before the kickoff it was announced that such drinks will be prohibited for the rest. I would rather blame FIFA for this fiasco. It was their responsibility to make sure that fans are being treated well. But then, FIFA didn't uttered a word against Qatar, when they made all these changes to the existing plans.