Really sad. They are doing something to improve their lives, they went where they could afford the surgery, and this happens.
The risk with leaving the USA for medical treatment is that doctors are gods elsewhere. They can’t be sued. It is a protection for our patients here.
There are two sides to this, which makes it tough for those trying to get help on a budget. You are completely right, and it's sad that they were trying to do something to improve their health and this happened. However, I wouldn't even drink the water in Tijuana. I'm surprised that anyone is desperate enough to try elective surgery there. I'd choose to keep the excess weight (even with all those risks).
If we truly had a free-market healthcare system nobody would need to go overseas.