https://en.wikipedia.org/wiki/Proclus

Proclus Lycius (/ˈprɒkləs laɪˈsiəs/; 8 February 412 – 17 April 485), called Proclus the Successor (Greek: Πρόκλος ὁ Διάδοχος, Próklos ho Diádokhos), was a Greek Neoplatonist philosopher, one of the last major classical philosophers of late antiquity. He set forth one of the most elaborate and fully developed systems of Neoplatonism and, through later interpreters and translators, exerted an influence on Byzantine philosophy, Early Islamic philosophy, Scholastic philosophy, and German Idealism, especially G.W.F. Hegel, who called Proclus’s Platonic Theology “the true turning point or transition from ancient to modern times, from ancient philosophy to Christianity.”^[1]

Upon review of this, you can see the decline of Pythagoras’ work to this “Transition.” Multiple signs are apparent that show the True Philosophy is lost. 

References in this text are made about Proclus’ struggle to find “Adequate” instruction: 

He studied rhetoric, philosophy and mathematics in Alexandria, with the intent of pursuing a judicial position like his father. Before completing his studies, he returned to Constantinople when his rector, his principal instructor (one Leonas), had business there.^[4] Proclus became a successful practicing lawyer. However, the experience of the practice of law made Proclus realize that he truly preferred philosophy. He returned to Alexandria, and began determinedly studying the works of Aristotle under Olympiodorus the Elder. He also began studying mathematics during this period as well with a teacher named Heron (no relation to Hero of Alexandria, who was also known as Heron). As a gifted student, he eventually became dissatisfied with the level of philosophical instruction available in Alexandria, and went to Athens, philosophical center of the day, in 431 to study at the Neoplatonic successor of the New Academy, where he was taught by Plutarch of Athens (not to be confused with Plutarch of Chaeronea), Syrianus, and Asclepigenia; he succeeded Syrianus as head of the Academy in 437, and would in turn be succeeded on his death by Marinus of Neapolis. He lived in Athens as a vegetarian bachelor, prosperous and generous to his friends, until the end of his life, except for a one-year exile, to avoid pressure from Christian authorities.^[2] Marinus reports that he was writing seven hundred lines each day.