Can you explain why for Muslims turning from Jerusalem and facing Mecca is called a symbolic break with the past?

It was, in fact, not a break from the past. Jerusalem is still a sacred city for the Muslims. Islam is the continuation of Judaism and Christianity. The Muslims must believe in all the Prophets (May peace be upon them all). It was the secret wish of the Holy Prophet Hazrat Muhammad SAW that the House of Almighty Allah, built by Hazrat Abraham AS should become the Ka'abah for the Muslims. His wish was granted by Almighty Allah.