I think O Mara’s seemingly nice guy image is one he has honed when being a TV analyst..and he does the ‘nice’ thing on purpose for the cameras.
As in, “Aw goly shucks..I guess we just don’t have the evidence. sorry.”
O'Mara comes off as a nice guy, but also comes off as very well prepared and always in control. That bail hearing sent a message that he's quite capable of being tough in court.