Zurich airport has an excellent train service to all over Switzerland, including trains every 30 mins taking 1h15 to Bern. Zurich also has a high frequency air service to London City - up to 11x per day against Bern's 2x per day
While Bern has a direct route to London City, there is a clear reason to choose Skywork for passengers travelling between London and Bern or the Bernese Alps (think skiing). Lose that connection to LCY, and the high frequency to Zurich becomes a lot more competitive, to BACF and Swiss's benefit