You're correct, anon. For Avenatti's case had to have been in the works for months, and the indictments unsealed in a carefully timed manner. Orchestrated.
In large criminal cases – criminal enterprise / RICO especially – strategy is to roll 'em up from the bottom of the pyramid / outside edges of the net, smaller fish first. Puts increasingly greater pressure on the bigger fish.
I'm taking the Avenatti indictments as an important marker. The very first indication of more to come.