Unfortunately they bury the meatier sales pitch in the documentation instead of putting it front and center on the home page: https://docs.onyxlang.io/book/philosophy/onyx.html and perhaps also https://docs.onyxlang.io/book/philosophy/wasm.html and https://docs.onyxlang.io/book/philosophy/memory.html

Basically, it's really all about certain WASM use cases, and everything right down to its memory management strategy is optimized for those cases.