Babcock absolutely knew what he had... however, his insistance of being inflexible and doing things his way was not the answer. Sometimes knowing what the situation is doesn't mean you are the one to fix the situation, and that was extremely evident with old Mikey. He was what we needed for the time he was here, but should have been let go a little sooner than he was... but hiring him and firing him were both the right decisions.
Keefe's system is posession... and only possession. We saw how that can break down in the playoffs, so the answer as others have noted is to have your go to, which can be posession, but you need a fallback that you are also comfortable with... could be dump and chase or whatever works for your particular roster. Tampa is a perfect example of that, and I think Toronto is on the right track to have a flexible lineup that can have success in playing multiple game styles.