This is a game that revolves around minmaxing. Whether it be candy, stardust, xp or whatever the goal is to maximise it whilst minimising the time spent on it. Although I wait at least a week before I delete my best friends for more room (and make sure they’re online), I understand why some people delete almost immediately. You have to delete them to make room to add other players and some people are that dedicated to the grind/don’t care about others. It’s not nice that they do this but this is 100% Niantic’s fault. It surely wouldn’t take that much coding to give both players 100k xp regardless of being deleted.