When Michael and Vito are doing their "playing dead" trick, they disband Sonny's regime and refuse to allow Tessio or Clemenza to rebuild their own crews. Presumably Tessio's and Clemenza's crews are full of slightly older men and may be suffering morale or even desertion problems.

As discussed this is all to make their enemies underestimate them.
Behind the scenes they have Rocco building a secret regime.

Also (as mentioned more in the novel) Vito has transferred his political power to Michael, who may even have expanded it beyond what his father had. Vito thought that "political connections and power are worth ten regimes".

My questions (and I don't know if there is a "right" or "wrong" answer) are:

1) How in the world did the Corleone enemies not notice a new group of "qualified" men coalescing around Rocco? Maybe this would have gotten past Tattaglia but shouldn't Barzini have been paying closer attention? Where did all of these people come from? Trained killers have to get started somewhere. Also how was the Corleone hierarchy paying these men?

2) How did the political power translate into the crushing of the Corleone enemies? Could it be that Corleone judges or police revoked licenses to operate or ignored murder investigations?

Thoughts?