Animal trials are important in medicine and science as a whole, and casualties happen. We have ethics standard to minimize suffering and loss. Especially when doing primate trials. They are generally treated as humans would be in an emergency experimental procedures. If you lose a few, it’s acceptable, so long as suffering was suppressed, and all reasonable avenues to save the animal were explored. Also, primates are hella expensive, so you generally can’t afford to kill them on a whim.

No, animal trials aren’t the problem. It’s that the company basically disregarded these practices. Last I heard (and this was last year), they burned through 15+ primates out of 23 test subjects. These creatures suffered fungal and bacterial infection, were left to tug at the implant leads causing damage to their tissue and the device, had the device fail during implantation and had broken pieces lodged in the primate brain for over a week before deciding to euthanize. Absolute carelessness, and disrespect for these poor creatures.