In Lost I thought the man in black could leave the island after Jacob dies so why didn't he leave once Jacob was pushed into the fire pit and died?

In "Lost," the Man in Black, also known as the Smoke Monster, could only leave the island if he found a way to escape his human form and the constraints imposed by Jacob. Jacob's death did weaken the island's protections, but the Man in Black needed to ensure that the remaining candidates were eliminated to fully escape. Additionally, he was bound by the rules of the game established between him and Jacob, which limited his actions until he could orchestrate the perfect opportunity to leave without being stopped.