Everything you said is true. There is also the fact that the second she declares, all guns will swing in her direction effectively ending the vetting process on all of the other candidates. Lots of damaging stuff is emerging on opponets, why interrupt the process now?
Good point, except that it won't be just the guns swinging in her direction. It will also be the lion's share of the eyeballs, column inches, campaign donations, supporters, etc.
She's going to suck the air away from the rest of the candidates, effectively ending many of their bids for the nomination.