He did not account for Archanfel's interference. And why should he? He had never met him. And if Archanfel had interfered just six hours later - if he had been hibernating - then Guyot would have succeeded. The Guyvers were unaware of the existence of the Remover, and if, as you say, he had not been drained by his battle with Archanfel, the only one who could realistically have stopped him was Barcas, about whose true battle capabilities we know nothing. But he did not transform when Archanfel was in mortal danger from being sucked up by the black hole, so...