Dumb Foreplay question

I had sex with an old guy friend whose had a crush on me since high school.. he stuck his 2 fingers in my mouth and I’m really trying to understand why he did it.

😂😂 I’ve never had anyone do that before but he seemed to really enjoy his 2 fingers in my mouth and I’m now really trying to understand why this is a thing and what it does for them? To me it can be sort of unsanitary being that you touch millions of things all day with plenty of germs and phones 😩 anyway at the time I was like umm 🤨 okay and, we just proceeded but why is this a thing??? I’m really trying to understand is it like a dominant alpha male thing or what? It has to be something though if you know or have any ideas pls respond thank you.

( no rude comments pls 😌 if you got no input you don’t have to respond, thanks for reading anyway )