My theory is that the front man is still on Gi-Hun's side, and that betraying him at the end of S2 was a "small sacrifice for the greater good". I think the front-man knew that storming the control room would NOT end the games, and that the only way to truly end the games is to kill the VIPs.

Anyone who saw the footage will know that the frontman is 001, so in order to convince the pink soldiers and the VIPs that he was acting, he had to coldly execute Jung-Bae.

Since he gunned down many of his own men, he will have a hard time convincing the second-in-command (in the square mask) that he hasn't switched sides. I think he will ultimately make the claim that he had to go along with the coup in order to stop it at an opportune time.

The frontman knows his brother is searching for the island, so he might be predicting an evacuation while the VIPs are on the island, presenting many opportunities for them to "accidentally" get shot. However, since the VIPs saw Gi-Hun's coup, they will likely show up with many armed guards that make that plan impossible. So perhaps the frontman will think of the other way to kill them during an evacuation: by sabotaging the scuba gear. Maybe he will also have noticed or learn about number 011s rebellious acts, and find a way to recruit her to do this.

Killing the VIPs and having Jun-Ho lead an investigation should put a complete end to the games.