Being the last man standing. Seems sad but when people leave bad company, usually the people who stay get promoted and some of them become senior developer. I have seen this strange pattern a few times.
When things inevitability go wrong, you'll also be the hero that powers through the weekend hacking a solution together. Be sure not to document or comment this code. It makes your memories critical to the operation of the business.
Eventually everyone else but people like you will move on. You'll be given a bigger say in the org by default AND you'll think exactly like all the other senior engineers. This will make you appear to be good at communication and working in teams since you can all say and do what you were already thinking.
Anyway, a company who puts that person on the phone as one of the first points of contact has serious communication issues. It was an easy pass for me (I already work in a company with broken communication).
I also usually ask "if someone has left the company in the last year" or so. However, they might lie, but most of the time they are not prepared for such a question. Reading micro-expressions (I am trying to learn...!) and the tone of the voice might help you with that, so that you can dig in and put some pressure to get some truth out of it.