TThis is really circular argument. You are arguing from your own acceptance of what constitutes true dharma without any hard core evidence. Just because sutra XYZ said this and that is not sufficient grounds as proof that it was expounded during the Buddha's earthly lifetime.
I would hope that you would read what I have actually said! Long ago I said that the Sravakayana was invented afterwards, and then mostly by worldy powers for political purposes. Recently I said that there appeared obstacles and impediments in the Sangha, in the spiritual careers of Buddha's disciples. I implied this earlier by stating that the buddhist sangha went through phases of development, deteriorating, discouragement, dispersion, efforts at renewals, etc.. And that this includes also the Arhats. Now recently I repeated this by saying that there were obstacles, and because of the obstacles new teachings like the Mahayana became necessary, and because of them the Mahayana doctrines were taught.
I have certainly read what you wrote very careful, and your theory have plenty of holes. First, you have given outlandish theories without backing it up with any historical or even scriptural records, such as your idea that during the Buddha's time there were obstacles in the Sangha. So what kind of obstacles, and where did you deduce that? Is it just your gut-feel? Second, you mentioned that those possessing abhijnas can easily verify for themselves what the Buddha taught back then - so assuming that there were indeed Arhats that came later and only learned the Sravakayana, they would have easily entered samadhi and see for themselves what the Tathagata physically taught, and it won't be difficult, since only a few generations passed. Third, you said "Sravakayana was invented afterwards, and then mostly by worldy powers for political purposes", but a few posts back you said:
Hinayana was a politically acceptable creation of some later arhats, it was created purposefully by arhats who were a split-off group from the original teaching and the original community.
So you consider Arhats to be worldly powers? This is ludicrous.
Saying that Buddha Shakyamuni had explored that realm of samadhi to a vast extent, and that these different samadhis were then expressed in the Mahayana, is not a circular argument. Because there is a continuation of these samadhis through the historical existence of Buddhism, this constitutes yet an other evidence.
What evidence? Samadhis are just numinous states, and these samadhis can just as well be taught much later when Mahayana sutras appear in the scene. These samadhis prove nothing on the question whether the Buddha taught Mahayana during his earthly time or not. You are not making sense here.
There is also the evidence of the Three Dharmacakras: Because the existence of the three turnings of the wheel of Dharma was widely known the Sravakayana compilers had to include it in their sutras. So they invented a teaching that it means that Buddha Shakyamuni taught the Four Noble truths three times!
Point to me where you read about these three turnings of the Sravakayana.
Because there were wordly powers behind the appearance and development of the State Sravakayana, it became well known. And so in the Lotus of the True Law both versions of the three Dharmacakras are included. Actually the Lotus of the True Law also mentions Four Dharmacakras in the verse portion. And so we have also the Fourth Dharmacakra mentioned in the Lotus Sutra.
Mentioning the Lotus Sutra is not going to help here.
There are other things like this, for example: in the teaching of the Twelve Nidanas the third link vijñana means alaya-vijñana. Alaya-vijñana is what reincarnates, and it is where the first and second link are stored. Thus Mahayana is the original and true meaning of the Dharma.
Oh my goodness. The term alayavijnana only appears so much later during Asanga and Vasubhandu's time. There are earlier terms that are cogent with the alayavijnana, such as bhavanga (for Theravada) and bija (Sautrantika), but these are certainly not equated with vijnana and inserted into the twelve nidanas like you do here. Your theory doesn't even make sense, since the 2nd nidana is samskara (fabrications) - so you are saying the alayavijnana is fabricated each time?