Because he didn't know what the source was and started grasping at straws and started with the one thing he could somewhat control. It doesn't make it so. Tens of millions of flights and literally billions of hours of flight time have occurred with consumer electronics basically unregulated. They don't crash planes.
I have this rock I carry in my pocket. Since I started carrying it, I have never been attacked by a tiger. Therefore, my rock must prevent tiger attacks.
By making your last statement, you have made the same kind of false correlation, and demonstrated you don't understand the problem.
US airlines have a great safety record because the FAA and the operators have implemented policies with redundancy in depth. A single error or failure won't crash a plane. But, almost every accident in the past few decades can be traced to multiple errors, compounding the problem.
Personal electronic devices have been documented to cause interference on multiple occasions. It didn't cause an accident, because pilots are trained to deal with even complete radio failure. But, the distraction could have easily been the first in a chain of events that led to an accident.