User blog comment:FairyRaven/Fairy Tail Chapter 416: Tartarus Arc: Final Part, Review and Commentary/@comment-174.64.108.169-20150119164125/@comment-9595671-20150119175017

I think in that case it was because the Tenrou Island team was thought to have been killed by Acnologia. When he learned Natsu and all of them didn't die he was happy again.