This passage uses the plural at the beginning and the end to refer to what was revealed to the brother of Jared, but in the middle the original text uses the singular to refer to “that which was made manifest unto the brother of Jared”. The 1920 LDS edition revised this relative clause to read in the plural (“those which were made manifest unto the brother of Jared”). Undoubtedly the plural works better in modern English, but the singular isn’t that jarring since the use of the plural them three times later in verse 5 can still be understood because of the plural things that occurs twice at the beginning of verse 4. The original text permitted such shifting in grammatical number within larger passages (see, for instance, the discussion under 1 Nephi 5:21 regarding the number for the word record in the text).
For this passage here in Ether 4, the 1920 LDS edition (as well as the 1907 LDS edition) edited “there never was greater things made manifest” to “there never were greater things made manifest”, which is consistent with other editing in the text: namely, in standard English there was is supposed to be followed by singular noun phrases and there were by plural noun phrases. The critical text will, of course, restore the original singular usage in this existential clause as well as in the following relative clause (“that which was made manifest unto the brother of Jared”).
Summary: Restore in Ether 4:4–5 the shifting from plural to singular and back to plural in referring to what was revealed to the brother of Jared; such variation in grammatical number occurred fairly frequently in the original text.