All aircraft have a WOW (weight on wheels) sensor. This disables many functions while the plane is on the ground. One of those things is to disallow unlocking of the gear. Further, for the gear to retract the plane needs hydraulic power. The only way to get that is with the engines running, not usually necessary on a pre-flight, or with a thing we call a MULE attached which is never used for a pre-flight. Further still, the gear is pinned when on the ground before the pilot gets in. That pin isn't pulled until just before the plane taxis or at what we call "last chance" just before take off.
So, for that plane to have collapsed, there were a lot of screw ups. I'm not saying I don't believe it happened, I do. I'm just noting how many things had to go wrong for it to happen. Also, the very first thing you do when applying power to an aircraft is check the down/lock lights for the landing gear. If you don't have three lights, the next thing you do is get out of the aircraft. Cycling the landing gear lever is really bad advice.