It's not.
Light was a loser from the beginning.
He just lacked the means to show it off.
i mean you have to agree even tho he was lucky at times and full of himself his internal monolog and god complex did make us admire him a bit not as in he was right but more like we knew his way of approaching justice was flawed.. his justice had no moral basis.. it followed a linear and shallow route.. ie : if there is no evil in existence.. there will be no evil practiced and fear rules all
tho the theory itself is logical and honestly at a certain point in the future it would have adjusted the masses into order.. but we know things aren't that simple and nor is humanity.. you can't suppress people and hope that they obey if you don't have moral standards in place for them to obey and no dreg of redemption for them to be hopeful of.
the more you dig the more you realize that even tho he did it for the "greater good" he still fell short on realizing the complexity of humanity and many other loop holes like a world where he has such a power other's do to.. and if someone with that power is oriented against him due to his way of "order" then Light's dream is doomed
L on the other hand has no way way justice that he was a fan of, what made him such a great antagonist was the way he dealt with light.. and played with him just a mere Detective that relationship between him and Light was the apex of the story.