Yes, “as” is shorter than “because, and it’s even shorter then “since,” and I generally recommend the shorter word when you write technical material, but in this case, don’t! Here’s a bad sentence:
Melorheostosis is one of the most notorious diseases as the reason for its occurrence was a mystery.
“As” means something like “at the same time,” or “while.” But the intended meaning here is “because.”
So use “because”! Use the clearest words to say what you mean.
PS—Here’s an unrelated sentence where the writer gets it right:
It was dubbed dark matter because it does not emit light, but it is also mysterious: it is not composed of atoms or their usual constituents like electrons and protons.
Isn’t that better? Less pretentious.