there's a balance to be found between over explaining to the point of condescension and under explaining to the point of hollowing out sentences into cryptic word puzzles
but man, please lean toward the former if you want to communicate and get points across bc whew some people

mostly talking about this when it comes to interpersonal/professional/casual relationships
in a teacher-student relationship it's more obvious you should go the over explaining route, because it's literally the point of you being there

in professional settings, there's a natural repulsion some people get when someone is over explaining something to them, especially by people who are often stereotyped as being unqualified, even though they might be experienced, because it feels like they're assuming you're dumb

but, the chilling effect of "please assume I know everything" leads to very bad communication long term, because you run the risk of making people scared to use clear language, and thus miscommunication and mismatched expectations will cascade