Lol it was just so random like everybody had a gun. Oprah must have gave them out before the mission.
I think the scene was to show Krakoa will be around for awhile. Kid Cable specifically asks if it's worth it and Cable is like you want to know if Krakoa will be around forever, well fight for it. So we know at the very least Krakoa was around long enough for Esme to become an adult and reunite with cable. I thought it was cute how she still has a soft spot for kid cable and told adult cable to go easy on him.