Einstein presented his theory of relativity in 1916, but for an entire century nobody could find physical proof of black holes. In 2016, scientists finally detected gravitational waves that emitted from 2 black holes colliding, proving that such things not only exist, but that Einstein was right all along. Source
At one point Einstein himself said he was wrong about black holes.
Which means Einstein was wrong about something! He was wrong about being wrong!
Really we’ve known black holes existed for a while, but we had no idea what kind of physical properties they had. This brings us a step closer to establishing which kind of black holes exist. Maybe there’s more than one kind? There are several physical possibilities. My favorite are the fluffy ones.
Black holes are like the higgs boson. They do exist and everyone accepted they existed, there was just no real proof until recently.