Why does he bless Hashem?
Rashi: It is for all that He did for us.
Radak #1: The author saw with Ru'ach ha'Kodesh Yisrael's return from Galus, and thanks for it.
Radak #2: The author says so amidst finishing the Sefer 1 , like I explained above (refer to 41:14:1:2).
Malbim: He will guard His Emunah, and His promise will be fulfilled forever.
This completes the third Sefer of Tehilim. Verse 1 attributes this Mizmor to Eisan ha'Ezrachi! Radak (1) says that he was the son of Zerach ben Yehudah. Presumably, he died long before David, who composed many Mizmorim in this Sefer! Perhaps David added this verse to complete the Sefer. This is not difficult if we say that David composed it for Eisan to sing (he was not Yehudah's grandson; refer to 88:1:5:1, 89:1:2:1. - PF)
