Unclear how Brad will do in attracting FAs and making trades, but I do believe Ainge's DRAFTING got significantly better when Brad joined the organization, and it sounds like Brad was excellent at doing due diligence and analyzing college players (which makes sense based on his ability to spot diamonds in the rough when recruiting HSers as well).
This also allows us to take a chance on an up and coming coach and, if Brad needs to pull a Pat Riley and take over the reigns at some point, he can.
Unclear how this will turn out, but I imagine the players feel strongly about Brad (in a positive way) and the org. felt keeping him around was good for continuity (and hopefully more).