Was it clear to the prophet's (SAW) people that there would be 12 shia imams after the prophet?

Salamun alaykum Shia brothers. I want to be educated on the matter of 12 imams. I don't want to offend anyone or mock any beliefs, I pose this question and set of points as I want to receive answers. My question is, did the Prophet (SAW) and the 12 Imams really make the concept of 12 Imams clear to their people? I contest this with 3 points: 1. We have 10's of 100's of hadiths and quran verses about Salah, Zakat, Hajj, Tawhid and Prophethood. Through this repetition, we're sure about the necessity of the 5 pillars within Islam. If the concept of Imamah was essential, it would deserve the same repetition by the Prophet (SAW) and 12 Imams in hadith literature 2. On the Hadith of 12 successors , it talks about caliphs instead of imams, doesn't mention names and says they'll be from the clan of Quraysh when the 12 imams are strictly from his (SAW) progeny. The Hadith doesn't make clear who these 12 successors would be. 3. Throughout history, many Shia sects came and went, and many branches still exist today. If the Prophet (SAW) and Imams properly conveyed Imamah to their people, why such differences between the Shia sects on the matter of Imamah? They all have their own Imams, with no set of Imams having more evidence than the other (According to my knowledge). In Shia sources, does each Imam narrate a hadith where he clearly appoints the next Imam? Thanks in advance for your answers.