A couple of thoughts on this in no particular order:
1) This animal weighed 200 pounds, and from what I understand chimps are about three times stronger than a human of the same weight. Bad idea to keep an animal which might require three or four strong men to control.
2) Yes, chimpanzees are highly intelligent, easily trained, and can seem almost human at times. And this is exactly what makes them dangerous to keep as pets. Sooner or later any intelligent animal will want to live as it pleases. This can and does result in unpredictable behavoir. Human adolescents are a perfect example. This animal was of the age when he was reaching sexual maturity and also asserting his independence. Picture an out of control adolescent human, but with three times the strength, and lacking a brain to fully comprehend what was going on, yet possessing far more intelligence and dexterity than a cat or dog, and thus to some extent having the ability to outwit those seeking to control him. He likely saw the woman's friend as a threat even if he may not have exhibited this behavoir in the past.
3) Giving Xanax even to a human isn't a particularly good idea. Like many other psychoactive drugs of this type, it causes more problems than it solves. Results are at best unpredictable, and often dangerous. Giving such a drug to a simian with different even if close body chemistry is about as stupid as it gets. She may have changed her story and said she didn't give him Xanax, but I for one don't believe her.
4) It's a shame the police didn't have less lethal means to subdue the animal. I might have thought knowing they had a resident who had a chimpanzee that they at least might have tranquilizer darts. And for that matter why didn't Travis's "owner" (I use the term loosely as I don't feel one owns a pet) have something with which to subdue him. Charming or not, fact is he was a 200 pound animal with massive strength. There is always the possibility he might get out of control. Seeing that I might have trouble subduing an 8 pound house cat hell bent on attacking me, I couldn't imagine dealing with an angry 200 pound chimp. In general it's not a good idea keeping animals you can't physically control, but if you must, have some preferably non-lethal means of controlling them.
Poor Travis died on account of his owner's stupidity in thinking she could keep an intelligent, social but still wild animal as a pet. He should have been with his own kind.