Read the following excerpt from Mark Twain's Life on the Mississippi.
When his boat blew up at last, it diffused a tranquil
contentment among us such as we had not known for
months. But when he came home the next week, alive,
renowned, and appeared in church all battered up and
bandaged, a shining hero, stared at and wondered over by
everybody, it seemed to us that the partiality of Providence
for an undeserving reptile had reached a point where it was
open to criticism.
How does Twain use irony in this excerpt?