It's been explained just how it can. By me, by others. What caused the separation of the trim tab will be interesting to learn if possible.
I think what they were getting at is maybe the changes made to the plane made it much harder to control once something did go wrong. Granted these planes are built to do 1 specific thing and that's go fast and turn along a racing course but you can't say cutting 5 feet off the plane's wings as well as reducing the control surfaces is not going to affect how the aircraft handles.
You can't really treat this like a normal aviation accident because normal planes fall under known specifics as far as their testing and so forth. These types of mods greatly affect how the aircraft flys and who knows how it would react once something breaks.
Not trying to vilify the guy as I'm sure he was a great person, it's just this accident should be a wake up call if nothing else that things need to be looked at a bit closer with these type of events. The same bad things have happened in auto racing over the years and because of the accidents racing has become safer for both the drivers & the spectators. Early races for example, drivers used to show up with roll cages built out of wood and spectators used to line their cars or stand along the edges of the tracks. (morons still stand along the track sides in droves in off road racing & rally racing)