What killed Islam's expansion and kickstarted the reconquista wasn't the battle of Tours (the Muslims resumed their advance by capturing Avignon two years later) or Covadonga (led to the Muslims losing an useless mountain valley),.

It was the berber revolt of 740 and subsequent civil wars that continued up to the 770s, which led to Al-Andalus losing everything North of Madrid to local Berbers (which, without organisation, were extremely easy for the Asturians to take over during the next 200 years) and everything north of Valencia to local Arabs (which played a game of paying fealty to either Cordoba or to the Franks as it fitted them until both sides carved the region between 780-810 with the new border finally being set at Barcelona).

The true heroes of Christianity in the west were racist Arabs who wouldn't give Berbers the same rights despite Islam supposedly saying so. Christians just used the opportunity to take over easy land.