Here the 1874 RLDS edition changed came to did come, probably because of the use of the auxiliary verb did in the surrounding text (“did go before them and did talk with them … did travel … did build barges … did cross many waters”). The 1908 RLDS edition restored the correct came. For another example of this error in the 1874 edition, see under Mosiah 28:5. As explained there, the Book of Mormon overwhelmingly prefers “it came to pass” over “it did come to pass”.
Summary: Maintain in Ether 2:6 the original instance of “it came to pass”.