You're kidding right?
Oh wait, no you aren't. They helped COVER IT UP, so why would they whistleblow themselves?
The other reason is, many of them want Trump to keep in power either to save their own skins, or protect their interests.
Way I see it, they told the whistleblower because they KNEW they couldn't risk themselves being called out (and they had no ballz themselves to do it) so they told someone whose job includes security stuff so he or she could do the job.
I mean, come on, not every human is morally righteous, remember