You cannot look at each piece of evidence in a vacuum and then say, well here is some possible alternative explanation for this piece of evidence, let's move on to the next piece of evidence. You need to look at the entire picture that is painted and ask yourself when you put it all together it is reasonable to doubt that she murdered her daughter.
She tried lie after lie to explain her daughter's disappearance. Eventually, after a couple years, she came up with a tale that was implausible but not impossible. Is doing that enough now to get people off for murder? Just about any murder case could be explained by some implausible alternate tale. Supposedly this was an accident that was made to look like a murder? When is that ever done unless to frame someone? And why would they do that? Children drown in pools frequently. And her father, who helped secure her representation in the first place, would prefer her daughter be convicted of capital murder than to admit that he helped cover up an accident?
Again, I will reiterate that people are convicted of murder frequently when a body is not even found. Her daughter was missing for a month while she was partying and acting as if nothing was wrong. It was not until her mother called the police that Caylee was reported missing. Casey Anthony ditched her car, which smelled, according to multiple people, like a rotting corpse. There was evidence of decomposition in the car. Because there could have been more evidence of decomposition, that should allow you to doubt the rest?
Some of the jurors and others focused on the fact that a motive was not proven. First of all, that is not even an element of the crime the prosecution needs to prove. Secondly, the prosecution provided one that was totally consistent with Casey Anthony's actions and her behavior. Some expert referred vaguely to people mourning differently after certain traumatic events. It is telling that this expert had not even interviewed Casey Anthony to provide any support that the theory was relevant to this case.