Why is it so do difficult for some to just acknowledge that certain civilizations in the world did contribute somewhat to the knowledge we have know?
Nowadays opinion about Islam is very polarized. The same can be said to some extent in historiography. Just because Muslims are frequently viewed negative these days, decades long contributions of 'Arab' science (I used the word Arab since the lingua franca was Arabic in those days) are simply denied.
It's certainly not true Arabs only borrowed from Persian, Indian or Greek knowledge and passed it as their own. Just have a look at the commentaries and additions Arab philosophers made on the ancient Greek sources. Or the refinements and calculations Arabs (Al-Tusi and Ibn Al-Shati) made on the works of Greek astronomers.
That said, there is no such thing as "Muslim" inventions. Was it religion that specifically introduced certain scientific concepts? No simply people in a particular society that happened to be Muslim. And it's true of every other religion. There is no such thing as Christian science, Jewish science or Hindu science. Religion cannot introduce anything other than religion; only people introduce new concepts and innovation.
To the contrary my friend, Persians, Indians and Greeks, borrowed from Arabs before Islam, Mecca is a testimony to that, besides more than 15 Arab civilisations in the fertile crescent -Mesopotamia- and the Nile valley who have coexisted with the Indus valley civilisation.
They knew of astronomy and Mathematics way before the Greeks, they were navigating the Arabian Sea and beyond as well as navigating their ways in the desert, which is no small feat, since it needs a thorough knowledge of astronomy at least.
After all, the Pyramids of Egypt contain much known mathematics, geometry, astrophysics and much beyond in the scientific fields up till now.
If you search on the Greek temples, you'll find out how their pylons are pure copies of the Egyptian ones.
So the Arabs just continued their discoveries and innovated on them after the venue of Islam, while benefiting others at the same time.
There were some "lazy" periods for the Arabs due to some difficult circumstances from time to time, but they always came back and started anew on improving everything they can, we can even see it today that they are coming back again with Islam as A very powerful motivational tool based on faith in the Creator and deep respect and understanding of his stunning laws of nature and the universe.