To be fair, that's how many theories work. Einstein didn't have sold evidence for half of relativity, just a notion and the math to support it. Later, when technology advanced to prove it, it became accepted as fact. Part of it continue to be proven today.
Which is the point here, just because it is a theory doesn't mean it isn't true ... BUT it also means no one believes it until solid evidence is shown for the hypothesis. They don't act on it or put people's lives in chaos without proof.
If ole Rudy there was on trial for murder and they were moving to convict over "theories" versus evidence, he'd be having a full blown hair dye melt down. But with Trump, he expects people to just believe and accept the theories as facts.