Brutus said there is a tide, but his action leads to defeat, not fortune, right?

That is indeed correct. Brutus is trying to justify engaging with the enemy at Philippi, as he believes that it is somehow fated to happen. But he is sorely deluded—just as he was when he allowed himself to be played by Cassius, who pandered to his overwhelming vanity, making him believe that the best people in Rome were crying out for him to take over.
By ascribing Caesar's assassination, as well as the outcome of the forthcoming battle, to the forces of fate, Brutus is trying to minimize his responsibility both for murder and potential defeat. If it was all indeed fated to happen, then much the same could be said about Brutus's eventual downfall and death. Even if Brutus is right about a "tide in the affairs of men," it would appear that he has miscalculated it quite badly.