If the hypothesis is adequate to begin with, then the explanandum follows from it. The indirect method is to ask what other consequences would follow. Having first reasoned backwards from explanandum to hypothesis, we now reason forwards, drawing further conclusions from the hypothesis and checking to see whether the conclusions are true.
If one or more of the consequences we derive from a hypothesis turn out to be false, then the hypothesis can be rejected, in accordance with the hypothetical syllogism.
The fact that a single consequence turns out to be true does not prove the hypothesis true. For confirmation, what counts is the number of consequences we test and their relation to the various alternative hypotheses we've considered.