As explained under 1 Nephi 2:14, there has been a minor tendency in the text to replace did do with did, namely, by Joseph Smith in his editing for the 1837 edition. Here in Ether 11:14 we have one of those examples; another example is found in 2 Nephi 5:18. And there’s also an example, in Helaman 13:24, where do do was replaced with do. There are other verbs for which Joseph removed the auxiliary verb do, but those cases seem much more idiosyncratic (see nearby under Ether 11:5 for discussion of this point).
Here in Ether 11:14, the critical text will, of course, restore this instance of original did do. Note that nearby in Ether 11:10–11, two instances of original did do were not emended (the text reads invariantly in both cases: “and he did do all manner of iniquity in his days … and he also did do that which was wicked in his days”). For a complete discussion of this archaic usage in the original text of the Book of Mormon, see under do auxiliary in volume 3.
Summary: Restore in Ether 11:14 the original use of the archaic did do, the reading of the earliest text.