Mahayana revealed from Naga world to 1st century CE+ - Why?

If I take these definitive positions: 1. Mahayana teachings did originate from the Buddha and were taught to select disciples. (Whether in full or in part) And were then passed on selectively to various followers. 2. These teachings were, as tradition says, hidden in the Naga lands until the proper time for their dissemination arrived. 3. These texts/teachings began to appear around 1 BCE to the early part of the common era. Assuming all these religious accounts did happen as tradition states, is there a secular/academic/historical way of accounting for these events no matter how speculative? To be more specific, **what was so special about the early centuries of the common era (its culture, people, language, geo-political environment) that the Mahayana teachings had to be revealed at this particular point in time?** One of my initial thought was that the Buddha and his followers were living in a time were Prakrit wouldn't be the best language to use to disseminate Mahayana taught. It needed the developed Sanskrit of the early common era and Nagarjuna to reveal these "profound" teachings. But this may not be the case as per my exchange with Andrei. So I'm in the market for ideas...