Two possible scenarios:
1. This facility was made to shelter the families of ultra wealthy, the billionaires and their families. Billionaires often has a track record of being egotistical control freaks, with almost zero empathy about the concerns of others. They didn't amass that wealth by playing fair. People were exploited, screwed over, even killed. The facility more than enough for all of them to benefit, but there was a handful of them that has huge egos and pride they have to be in charge. Someone tried to do an Elon, and fucked it up for everyone. Now, everyone is dead.
2. The AI lied to the MC, and it was the one responsible for killing everyone. Even if there were groups vying for control over the facility, there has to be some survivors, assuming that they were families, even children in the facility. Trying to escape the facility is punishable by death. What other rules it has imposed that has same sentence? The people tried to band together to overthrow the AI, but failed. The man who took his own life probably did so after the AI wiped out everyone in the facility.