He argues that philosophers are wrong and that Allah is the only cause of everything so it makes no sense looking for other causes, i.e. Laws of Nature. Also, he was a proponent of Sufism, which is mysticist and a mystery society with a degree system like the later Freemasons, Rosicrucians and about any other occult esoteric society in the West (who all are modeled on Sufism in a way). So no public dissemination of ideas to be expected from those guys.
Well, his book was a roaring success; Muslims loved it; so they stopped doing science. How much of the “Muslim” scientific achievements of the Golden Age of Islam were actually made by Muslims and how many were just received from other cultures and collected in Baghdad is another question – “Arabic” numerals for instance were received from India.
The sacking of Baghdad in 1258 didn’t help either; but the question has to be asked: Even if Baghdad fell, there were enough places for Muslims to continue doing their great science – and maybe develop superior weapons to kick the Mongols out – but they didn’t. Why? Well because Al-Ghazali told’em that science is pointless.
And look at that in the 1258 link:
Initially, the fall of Baghdad came as a shock to the whole Muslim world, but the city became an economic center where international trade, the minting of coins and religious affairs flourished under the Ilkhans.
So they didn’t even bother much.
To this day, the lack of Muslim Nobel prize winners is testament to the devastating victory of Al-Ghazali over Islamic Science. He died in 1111 and had finished it off.
A bit more on connections between Sufism and the Western mystery societies: