Another point here: there was a fairly widespread belief that the moon, stars and planets were not affected by gravity in the same way as “an apple”. The concept of spherical (as in heavenly) material being fundamentally different was still considered roughly accurate. What Newton did using the new calculus (not getting into who came up with calculus in the first place) was provide a physical and mathematical model that would allow for an apple falling, and a moon stating in orbit, without positing that the moon behaved fundamentally differently.