The most likely, and least scientific answer is that you were doing your squats in a way that caused you to hit your Glutes more than you were used to. Now, I don’t know if you squat on a regular basis so I’m not going to say that that’s the exact reason but, DOMS is usually caused by performing a movement that you’re not used to performing or hitting a muscle that you don’t usually hit.

Here’s a link to an article that talks about DOMS in more depth: https://en.wikipedia.org/wiki/Delayed_onset_muscle_soreness