RE: Stupid question, why/how do planes fly inverted?
Same reason it flies right side up.
To fly right side up, the wing finds an angle into the airflow that creates lift. We can't see that angle from the ground.
Same thing upside down.
We usually can't see that angle from the ground either on most models. Some you can. In almost every case, to hold altitude when inverted, we have to hold down elevator. Think about that.