Tum ad sacerdotes creandos animum advertis, quamquam ipse plurimis sacris, maxime sacris Iovis, praeerat. Sed quia in civitate bellicosa plures Romuli quam Numae similes reges fore putabat iturosque ipsos ad bella, ne rege absente sacra neglegerentur, Iovi assiduum sacerdotem creavit qui 'flamen Dialis' appellatus est.
I'm perplexed by the phrase '..maxime sacris Iovis, praeerat' '...even though he himself most of all was foremost - then 'sacris' - with sacrifices ? and then for some reason we have 'Iovis' genitive? I can't work out why it's in this case.