you are misunderstanding how physics works. einstein didn't think up a bunch of different random ideas. he had a small number of very deep insights. various

you are misunderstanding how physics works. einstein didn't think up a bunch of different random ideas. he had a small number of very deep insights. various things follow from those insights - come out in the maths, if you like. gravity waves are just one way that his description of gravity can be confirmed. it's true that they are difficult to observe and so haven't been confirmed yet, but no-one expects them to not exist. at this point it would be hugely more interesting if they were not found than if they were.