This is also my guess. High heat causes the cheese to separate out its oil. My guess is the pasta water was too close to boiling. I bet if you try again but take your time it will work better. Let everything cool just a bit more and stir vigorously so you limit hot spots. Lots of different advice being thrown out, I hope one of them works for you!

For me it’s gotta be Deer Hunter. Saw it as a kid and it still fucks me up