Oh my God. What a simplistic way to treat a massive subject!
It was briefly the centre of the world my friend. From the first quarter of the 10th centre to just after the milennium. Then it all went wrong.
I cant go through explaining this 'Moors' thing all again. The Caliph united the various rebellious and disagreeing parts of Muslim Spain, and at times allied with christian states too. many of his subjects were christian, and many were converted christians. The 'Moors' (at this time, pre-Almoravid and Almohad) were a blend of cities and states ruled by and populated by rival arabs, yemenis, slavs, berbers, old visigothic rulers converted to Islam etc etc etc. Quite a mix. In Spain and Africa.
But at it's height the caliphate had half a million people in Córdoba of all races, and the best in every field. And a fair army!
Abderraman was actually related to many of the royal families in christian kingdoms through his mother's ancestry, and did a bargain to put Sancho the Crass back on the throne of León with the support of troops from the caliphate and christian Navarra.
The strength and power of the caliphate meant a bad time for the much weaker christian states in the north, who only recovered the initiative after it's collapse. Mind you they didn't have it all there own way. Whilst León had sensible kings early in the 10th century, there were reverses for the caliph like Simancas. But later, when Almanzor was in full flight toward the Milennium, the christian lands suffered greatly.
And just when it was at it's height, it collapsed, back into it's constituent parts.