According to Osho, many monks did attain Buddhahood, but they remained unseen because awakening and mastery are different. To awaken others, an enlightened one must descend to the seeker’s level and retrace the path—a distinct sadhana. Most are kevalis (knowers), not tirthankaras (masters). Hence no precise count; true Buddhas may not appear as teachers.
Many of Buddha’s disciples woke up, but most didn’t become teachers, so you don’t see them.