Why do hard CTF challenges get solved rapidly after the first solve?

Hey everyone!
I’ve been participating in CTFs (like those on CTFTime) for a while, and I’ve noticed something interesting: when a hard challenge gets its first solve, it often gets solved by a bunch of other teams shortly after.

Is there some kind of behind-the-scenes sharing happening? Like, are people or teams sharing flags, hints, or solutions in private communities? Or is it just that the first solve gives others the momentum to crack it too?

Just curious if anyone has insights into this! Thanks in advance.