To me it seems there are two different arguments for Occam's Razor.

1) Sometimes relatively short explanations can explain things about our universe. This seems to be a fact about our universe. There could hypothetically exist universes with extremely complicated fundamental laws, but our universe doesn't seem to be one of them.

If theory of relativity or quantum physics seem complicated to you, imagine universes where the similar equations would contain thousands or millions of symbols, and couldn't be further simplified; that's what I mean by "extremely complicated".

2) For every explanation "X", you can make any number of explanations in form "X, plus some additional detail that is difficult to verify quickly". It is better to just remember "X", until some of those additional details is supported by evidence. This does not mean that the additional details must be wrong, it's just... there are millions of possible details, and you wouldn't know which one of them is the right one anyway. Using the simplest option that corresponds to known fact is more economical.