What causes wet dreams after a long period without ejaculation, even without strong arousal?

I had a wet dream recently and I’m trying to understand what might have caused it.
I wasn’t very aroused during the day — I watched some reels, but nothing intense. Still, it happened at night.
For context:
I haven’t been sexually active or masturbated in about 2–3 months
I don’t exercise much lately
I’ve been eating more spicy/junk food recently
Could any of these factors (stress, diet, inactivity, or buildup) contribute to this?
I’m mainly trying to understand the biological reason behind it.