Mommaerts and Kelley have proposed a theory that Petronius Maximus, the successor of Valentinian III on the Western Roman throne in 455, was behind the marriage of Placidia to Olybrius.
Mommaerts dan Kelley telah mengusulkan sebuah teori bahwa Petronius Maximus, penerus Valentinianus III di takhta Romawi Barat pada tahun 455, berada di belakang pernikahan Placidia ke Olybrius.