Possible options:
- it only supports a subset of MediaWiki syntax, which is easier to handle and optimize
- git manages files better than MariaDB as used in MediaWiki
- MediaWiki needs more resources to function properly
- ...
PS: One more question: will it still be faster if a page have so many transclusions like Wikipedia?
I'm also trying to write a wiki software called LuaWiki. So I want to learn something from this project.