A very central aspect to the importance of the ancient texts was their entirely different view on humanity/ the human. To understand the importance of these texts and authors, one needs first to understand the mindset of the medieval world.

In the middle ages, most intellectual and spiritual thought was focused on the transcendent. Life in this world merely being a necessary precondition for the afterlife and all of your struggles and worries were justified in the persuit of eternal salvation after death. This is not to say, that medieval thinkers couldn't grasp the concept of the individual, but it was of very little importance. A plastic example would be the status of artists and artisans. In medieval times you often wouldn't really know about the man behind the work, the sculptures and freskos created in the honour of god were not the be a medium of agrandisement for the individual artisan, but were solely created for the glory of whom they celebrated (usually god or his highest servants on earth).

With the (re-)discovery of the ancient texts, the concept of individual genius reentered European thinking. If there was a concept of genius in Islam before, I sadly do not know, so I can't tell if it was a discovery or rediscovery for the islamic culture. Nonetheless, the humanities of antiquity were of an entirely dirrefent basis than the transcendency of the centuries before. Though one also has to keep in mind, that these texts not merely needed to be known, but also put in a fruitful environment to take root. Rich states with differentiated economies and the time and ressources to invest in art were a prerequisite for these texts to take root and the ancient humanities to reemerge and develope a new, renaissance humanism.

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To give you a contemporary writer, who dealt with your questions (and who is said to have coined the term renaissance most prominently), I recommend you to read Giorgio Vasari " Le Vite de’ più eccellenti architetti, pittori, et scultori italiani ".