Read the link. The magnet pulled the gun into it with enough force for the firing pin to hit the primer. This will happen to almost any gun if dropped hard enough and if it hits at the right angle. This is no mystery.
The whole R700 "thing" was a bunch of horse hockey gun grabber propaganda that was used as a base for lawsuits against Remington because some (several) idiots negligence. That load of bull was completely and fully debunked years ago.
Remington 700's have been discharging without pulling the trigger for 60 years. There have been thousands of documented cases. Remingtons own people discovered the flaw in 1946 and urged a trigger redesign. That load of bull was proven beyond any doubt to anyone willing to pull their heads out of the sand before most of were born. It has been common knowledge to anyone with any gun knowedge since the 1970's. Just because some guys just heard the news a couple of years ago they are convinced it is a plot by CNBC. CNBC reported nothing that hasn't been well known since before TV existed.