The reason for the trim switch on a control column to consist of two separate switches is - ATPL

Question id 72 - Aircraft General Knowledge - Airframe, Systems, Powerplant - ATPL - Airline Transport Pilot license

To reduce the probability of a trim-runaway

To Be Able To Use Two Different Trim Speeds, Slow Trim Rate At High Speed And High Trim Rate At Low Speed

Because There Are Two Trim Motors.

To Prevent That Both Pilots Perform Opposite Trim Inputs.