James Watt was only able to build efficient steam engines because Joseph Black discovered latent heat in 1761. Without steam engines, there’s no industrial revolution.

I read about Oliver Heaviside and that helped shed some light on engineering improvements from that period of time. He was around a bit later in the 1800s, though.

Yes, those engineers were inventing most things by themselves, but they didn't work in a vacuum.

As advanced as Ancient Greek mathematics was, its heavy emphasis on geometric formulations made many developments more difficult. The Hindu-Arabic numeral system, algebra, invention of a zero number concept (Cardan's proof of the cubic and quartic would have gone significantly easier if he had utilized zero as a number) and Descartes's Analytic geometry were important developments on the way to calculus. By the time of Barrow's and Fermat's contributions, nearly all essential components of calculus existed, just requiring some genius to grab, synthesize and streamline them.