How is a hypothesis useful?
Because it is a starting point for investigation .... it advances a proposition..
And an important property of an hypothesis is that it be TESTABLE, i.e. falsifiable. That is there exists a series of experiments whose outcomes would definitively confirm or deny the proposed hypothesis.
The better experiments are designed to test a simple proposition...do the data support this proposition? If YES the proposition, the hypothesis, may continue to be tested in other experiments. If NO, then the hypothesis is rejected, and it is back to the drawing board....