One scenario that I thought of requires a lot of "what if" qualifiers:
If George really were molesting Casey, many child molesters are not interested in adult women. Maybe George moved on to molest Caylee.
If George had been molesting Caylee and she died during an act of molestation or died as a result of an unrelated accident, George would, as a former police officer, know that her body would show evidence of the molestation.
If that is true, George would know how to deal with the body of Caylee so that it would decompose rapidly and evidence could not be found.
If George wanted to keep Casey from coming forward too soon, George could have known that blaming her for Caylee's death would drive Casey into a psychological state in which she would deny reality.
If George also wanted to implicate Casey, he could have put Caylee's body into Casey's car trunk.
This creates the situation: George HAD molested Casey and she was psychologically screwed up because of it. He molested Caylee, with or without Casey's knowledge. Something happened that resulted in the death of Caylee. George blamed Casey - classic "blame and shame the victim" and forced her to participate in the coverup. George puts Caylee's body in the trunk of Casey's car at some point, maybe wrapped it the same way he had wrapped dead pets over the years.
Maybe George intended to relocate the body sooner, but Casey goes into a frenzy of partying and does not return home for days when George is there. She did go back to the house on the two days after the death of Caylee, but that is too soon for the body to have been removed from the trunk and the death smell to be left in it. Or maybe one of those days is when the body was actually put IN the trunk? Whatever happened, the decomposition of the body is sped up by being left in the trunk in the Florida, but it leaves the odor as evidence.
George and Casey move the body into the woods. George washes his hands of the whole thing. Casey then is left to make excuses to Cindy about where Caylee is. She'd already created Zanny the Nanny and continues to use that story as long as possible. When Cindy is fed up with that story, Casey dredges up the name of an old classmate (can't remember his name right now) and makes up the Daytona Beach/Jacksonville tale.
George does not count on Casey abandoning the car and allowing it to be towed, or Casey could no longer stand driving the car with the stench. Casey or George or both leave the car at the Amscot parking lot, but leave fresh bags of garbage so there is some apparent source for the smell. The car is left by the dumpster so anyone walking by would blame the odor on the dumpster.
When the tow yard notice arrives, he has little choice but to go with Cindy to retrieve the car. With the tow yard operator there who recognized the decomp odor, George cannot deny it, though he probably tried to convince the guy that the garbage bags were to blame. George takes the car home and allows Cindy to clean it up, but cannot keep Cindy from tracking down Casey - Cindy with her experience knew what that smell was and was increasingly agitated. And we know what happened from that point.
This explains why an experienced former police officer would not report the smell of decomposition in the car; why he allowed Cindy to clean the car, removing evidence; why the body was removed; why Casey was so completely off kilter; why the whole family has been covering up everything. It could also factor into why Cindy and George were separated before Caylee's disappearance - Cindy could have been trying to protect her granddaughter from the things that she had not been able to protect her daughter from.
It still does not excuse Casey but it does give an explanation for some of the things that are not consistent with it just being Casey involved. It explains George's defensiveness and why he may not have told the entire truth to LE.
I thought of this plot before the verdict but discounted. Now I am wondering more and more if this may be what happened?