Try to keep things in historical context please. 13 was the age of majority for marriage in many states well in to the late 20th century.
That may be so, but when you're already married, whether your new wife is 13 or 31 is beside the point. One of the reasons he was run out of Kirtland, Ohio, was because of his philandering with other peoples' daughters and wives . . . besides his embezzling thousands of dollars from unsuspecting followers.
And if you go to the huge shrine built to him in Salt Lake City, you'll find a statue of him lovingly looking at his darling wife (#1 with 42 more to follow). Kinda' humorous when you know what a philander he was.
But none of the guides will talk about that.