Let's assume it is true and Sunnis followed Ghazali and stopped thinking, pondering and doing research work but what about Shias and other factions of it? Why did not they produce something amazing in science? One can't blame Ghazali for all the mess, especially when he was not followed by all Islamic sects. I will not blame Islam or Quran either. It is something else, probably some kind of excuse or laziness. I wanted to say that the "Hunger for Heaven" might have made them not to use brains but then I see non practising and liberal/modernist Muslims, they did not do anything remarkable either.
I guess it is a culture, some kind of viral disease like thought that propagated in entire Muslim world and it affected regardless of someone is practising Muslim or not. Being a Pakistani muslim I observe that people have no interest of asking questions, they never ask questions. They accept things as it is which is quite irritating. They just accept things as a "gift of God" and prefer to move on rather than finding out WHY is it around.