Gratitude to the Straw Hats for helping him realize his goal and freeing him from the eternal shade he was doomed to after eating the Devil's fruit? Like a surprising majority of the crew?
Also- it's a good thing. If you go by Luffy's "I'm gonna have a 10-man crew" formula, means the series should be ending soon-ish. At least we can gauge how far the story is, which is nice.