I think it's always important, when talking about Al-Alndalus - that even in works like The ornament, there is the temptation to selectively play up cooperative elements of the society and turning a blind eye to the fact that the general circumstances of the society are not one in which we as moderns would see as particularly 'multicultural' or 'tolerant' ; Scholars are good at holding these things in separation lay people generally muddle the two. Holding other religions as subservient classes is not in line with our ideals of modern religious tolerance.
I think its somewhat inevitable that pagan works would be lost over the centuries, and less surprising that they would survive in dryer climates. Ultimately, I think to make the christians look particularly oppresive and destructive one has to overlook a lot of pagan violence.
In the case of the islamic world, we can say for sure that there was a general destruction of churches, existing infrastructure and a general looting of most of the areas that came under islamic domination. And this is the pattern for the exchange of cultures nothing unusual. Taking the Dome of the Rock for an illustrative example - the Mosque at the dome of the rock began as a looted Marian shrine, built over the ancient roman temple which the romans themselves built over Herod's second temple.
I think it's useful to understand religious intolerance in a few tiers. The following tier-list is a sketch, but I think illustrates the idea:
Tier 1 (most intolerant): Suppress the out-group vigorously, including executions, torture, secret police, interrogations, etc.
Tier 2: Suppress the out-group violently (executions) any time they're noisy, but don't seek them out.
Tier 3: Disfavour the out-group, without permitting conversion.
Tier 4: Disfavour the out-group, permitting them to convert.
Tier 5: Disfavour the out-group socially and informally, but not in matters of enforced law.
Tier 6 (most tolerant): It's illegal to disfavour the out-group.
The reason I mention this is that modern notions of religious tolerance target maximum tolerance (Tier 6 or whatever), but there's a lot of variety through history. For example, I think that persecution of Jews under the Romans was, in some cases, only because the Jews were unwilling to also in-form-only obey the dictates of Roman religion (2nd Commandment makes that tricky). Contrast that with Nazi persecution of Jews, which was much more aggressive about seeking them out. It's worth it to identify that one of those is more tolerant than the other, even if we wish for our society to be more tolerant than either of those.
In that context, my understanding is that the Muslim law of the medieval period is pretty clear about tolerance, and that both Al-Andalus and Baghdad followed these rules. "People of the Book", i.e. non-Muslim monotheists, were granted a large set of very specific protections, while still being treated less well than Muslims. (Note that non-monotheists were not granted protections; I imagine that this did not result in much religious tolerance towards those people, but that's just a cynical guess.) These specific protections were strong enough that it made sense for non-conformist scholars (Christian or Jew, as long as they were monotheist) to migrate from Christendom to Dar al-Islam. Compared to modern west-coast notions of religious tolerance, this isn't great. But it's still remarkable and praiseworthy, especially in contrast with modern Sharia, and in contrast with then-contemporary Christian kingdoms.
In summary: it's not that medieval Muslim states were tolerant by modern humanist standards. It's that they were more tolerant than modern Sharia Muslim states, and more tolerant than medieval Christian states.
I think its somewhat inevitable that pagan works would be lost over the centuries, and less surprising that they would survive in dryer climates. Ultimately, I think to make the christians look particularly oppresive and destructive one has to overlook a lot of pagan violence. In the case of the islamic world, we can say for sure that there was a general destruction of churches, existing infrastructure and a general looting of most of the areas that came under islamic domination. And this is the pattern for the exchange of cultures nothing unusual. Taking the Dome of the Rock for an illustrative example - the Mosque at the dome of the rock began as a looted Marian shrine, built over the ancient roman temple which the romans themselves built over Herod's second temple.