>>281675892
At all steps, Light was foiled by his pride. That's one of the key themes of the story: pride leading to an unwillingness to bend or give in, and ultimately ends in breaking.
Light started off on the back foot because of his pride during the confrontation with L on tv. L died despite being sure Light was Kira because he refused to act on a hunch, no matter how strong, and that conviction led to Light outmaneuvering him via abusing the rules of the death note / shinigami. Light could've continued acting as Kira with a headless task force, but ended up making enemies of the SPK by acting as the new L. Even toward the end, Light and Mikami were convinced they had a perfect system, and it was through that 'certainty' that N and Gevanni had the chance to make a move.
It's the turnabout of this pride that provides the catharsis at the end of the story. Light, this man with godlike delusions reduced to a crying begging mess.