Realms deletes certain predicate files for "invalid json," despite being completely valid and working fine in vanilla. I am not 100% as to the exact cause, but I would guess it is not updated to accept the new 1.17 predicate formatting.

Attached is the main datapack experiencing the issue before getting uploaded, as well as the log file.

... and if I may make a suggestion, don't delete files because you think they're not valid. Developers may include comments or extra data that works with 3rd party programs. Empty files may exist to be overridden/extended by addon datapacks.