Nealy every civilization lost their repositories of knowledge at various points in their history. Usually what gets destroyed is not just the knowledge, the books itself, but the priests, monks, librarians, ... around it get massacred too. In all but a few civilizations, it only needed to happen once. In all where it only needed to happen once, it happened, through various means. Most often, it was an internal civil war. Other times it was external military conquest and plundering.

Greek, Roman and Western Judeo/Christian knowledge survived. Not because we never had civil wars that tried to destroy/eradicate it, or had plundering armies ransack libraries, but because there were 10 copies and only 6 or so got destroyed (or in some cases all but one). The copies happened because since the 4th century or so the Church decided to dedicate quite a few people to copying all knowledge (all knowledge, not just Christian) (and before the church state-sponsored educational groups did it). But the amount of effort should not be understated: you have to understand that this was first thousands then tens of thousands people entire lifetimes dedicated to nothing other than creating backup copies of physical documents, a massive cost to an economy that was a LOT smaller than today's.

The point is, most civilizations develop scientific knowledge. And they advance rapidly during the formative years of the civilization. Then things get frozen, and vested interests both prevent further research, limit access to existing research, and effectively lock up scientists, librarians, etc. Western civilization (and the Roman empire and a few Greek city states before it) did not do so, and instead dedicated large amounts of economic activity to science. This is completely exceptional, and of course, this is the reason that you're complaining about it, in the sense that you wouldn't be complaining about it had this not happened.

You should also keep in mind that the Mongol Empire advanced while driven by hunger, and Bishop Landa by overpopulation and lack of economic opportunity in Europe. The control those people had over whether or not to destroy things was very limited or even nonexistent.

For those various reasons blame should not go to the Mongol Empire or Bishop Landa, or any other conquering tribe/nation/country/..., blame rests with Islam and Mayans for the loss of this knowledge. They restricted and locked up their scientific knowledge, to the point of not having backups, and then their point of control over that knowledge got destroyed, along with all the knowledge.

Probably, a few families in those empires got to enjoy a very powerful position for a few centuries and in trade the entire state structure that millions depended upon got utterly devastated, including probably quite a few of those people.

There is a famous incident where the Caliph of the Islam has a written exchange with the remaining Crusader kingdoms, in what is today Lebanon. The exchange is the kings telling him that if he continues his attack, it may well succeed, but it would destroy the agricultural base that fed the millions of Muslims under his rule ... he acknowledges this, states that allah will feed them ... then attacks ... thousands die in the attack, and millions die from the resulting famine. The vast majority of the dead ? Muslims. Odds are good that the Caliph simply did not have the control necessary to stop the assault.