When it was invented, it wasn't "true", it was less false than the previous models, as it allowed to predict more accurate results than them.
The fact you call a scientific law an "evidence" just proves you have understood nothing of what science really is. It's a classic confusion amongts theists, so I'm not that surprised.
Evidences only give us hints about what the real world could possibly be. But again, evidences aren't the real world. Evidences don't lie, but you cannot make them say more than what they are supposed to be. And to find them, you have to seek them, they're not that "evident" for everybody.
Modern men just saw the effects of gravitation during hundreds of millenias, and even more. Yet, we were only able to name the phenomena very recently. Before Leibniz and Newton, we simply had no conception of what "gravitation" could be.
If you don't understand what I mean, here's an example:
Do you enjoy to see mountains or the oceans? Do you find them "beautiful"??
Well, our ancestors didn't. It was only during the late 18th century that Westerners begin to see them as "beautiful" through the process of "artialisation" (Cf Montaigne). Take Homer and the Odysseus... There is almost no mention of the sea, no description of marine landscapes. You can check it!
So what is "evident" for you is not that evident everywhere. And it doesn't mean our ancestors were stupid, obnoxious or daft.
It means Ideas have an history, a context.