Publishing an index.html works only sometimes

[AM2i9]

This is an issue that popped up when making the raffle page. The index.html was able to be accessed locally at /raffle, but once pushed and published, it could only be accessed by going to /raffle/index.html. It was solved by changing index.html to a markdown file, but why?

Other pages such as the donate page also use index.html, and they work fine.