The article didn't state that the C150 was towing the glider.
Yes, obviously somebody was lax with their scan. Airport is only a couple of miles to the east; one or both may have been arriving or departing the pattern.Those darn glider pilots! Always playing with their gadgets and watching TV! We need to keep our heads on a swivel and outside the cockpit people!!
Eyes outside + big sky + low probability = this will never happen to you.
Lot's of speculation there. The comments contain even more.Only reason I can think that a glider would catch on fire after a crash is that it has a self-launch or sustainer engine. Even then the engine is unlikely to have been running to have been an ignition source.
Also, a C-150 seems an unlikely tow plane (unless someone knows differently) so I'm skeptical that speculation is accurate.