Where did the idea of gravitational waves come from? (Patreon)

I will not to put too hard equations today, it's Friday btw
I am merciful😌

So Einstein’s chilling in 1916 and goes:
"What if gravity isn’t a force, but just geometry?"

And everyone’s like:
"What the fuck are you talking about?"

And he’s like:
"Yeah, stuff doesn’t move because it’s pulled, it moves because space-time curves like a drunk-ass road."

And then he’s like:
"If something massive moves, it should send ripples through that messed-up geometry. "