No one preaches that the Reinassance was unassisted, or that it was the source of all knowledge - but the technological development that allowed this boom came from Europe.
It's not by random chance that this creative boom came after the print press was invented - in Europe.
After it, the knowledge that was limited to a few people, was spread out via a media development: books, the medium that fueled all of this.
Leonardo was just curious, and had fuel to feed the curiosity, with answers.
It's questionable whether the printing press was an entirely novel invention. Movable type printing had been around for centuries in China, it was just less useful there due to the large number of pictographs. In fact one of the major innovations of Gutenberg was the alloy he used for the type that was both easily workable and durable in use.
Additionally, the major change people usually aren't aware of was the spread of papermaking knowledge through Europe around the 12th and 13th century. Before that point, most books were created on Parchment, which was much more expensive. I've read somewhere that a single bible took ~3000 sheep to produce.
But I didn't said it was a novel invention - yet it was indeed the European concept/invention that thrived and allowed for the boom in Europe.
Regarding the papermaking, I believe we can fit it in the same boat as other craftsmanship that evolved previously and allowing for the development for the press itself (but definitely papermaker had a greater role in some dimension - cost/manufacturing/distribution).
Sure. Good luck doing science without the scientific method in ridiculous impractical numerals, and printing books on sheep skin. Also good luck developing a theory of planetary motion without astronomic almanacs.
If you struggle, you can ask your highly educated peers (<1% of literacy at the time) to provide some help, or you ask the scientific elite at the time, a bunch of theocratic fanatics that would prosecute you, torture you and burn you alive along with all your findings as soon as you publish them.
Stop hoarding the credit. The Reinassance wasn't a self-emergent phenomenon. It required external influence to happen and that is factual.
It's not by random chance that this creative boom came after the print press was invented - in Europe.
After it, the knowledge that was limited to a few people, was spread out via a media development: books, the medium that fueled all of this.
Leonardo was just curious, and had fuel to feed the curiosity, with answers.