[Nik Naym]

“Not being a pilot, how do these type collisions happen?”

Simple physics, no two objects can occupy the same space at the same time. Pilots try to violate that law at their own peril.

[KevinB]

Simple physics, no two objects can occupy the same space at the same time.

Well, a couple of times a month my wife and I occupy the same space at the same time. Physics doesn't seem to cause a problem. :-)

[Does so]

I was called-in to investigate the same kind (high/low wing) of collision—back in the late eighties.

That fatal collison took place over the vast Everglades.It was strong enough a collision to knock a wing from the Cessna.