Found this Fudo Myo Sutra:
The Sutra Spoken by the Buddha on Arya-Acalanatha
At that time, in the Great Assembly, there was one Vidyaraja. This Great Vidyaraja possesses great majestic strength. He has the virtue of great compassion, thus he appears in a bluish-black body. He has the virtue of great meditative stillness, thus he sits on a vajra-rock. He has great wisdom, thus he manifests great flames. He grips the sword of great wisdom to destroy greed, anger, and ignorance. He holds the rope of samadhi to bind those who are difficult to tame. He is the markless Dharmakaya, identical with [all-encompassing] space itself, thus he has no dwelling. His only dwelling is in the minds and thoughts of living beings. The minds and inclinations of all beings are different. In accordance with the minds of living beings, benefit is given and what is sought for is attained. At that time, all in that great assembly heard this teaching and were filled with joy. Faithfully receiving it, they reverently put it into practice.
Emphasis mine. The bolded part of the sutra pretty much sums up my understanding of Bodhisattvas (and the non-historical Buddhas) as of today. Even if this is apocryphal (who hands out the seal of authority in these matters?) the author has a point that I happen to agree with.
One could easily admit that their parents exist. Other people exist, too, you met them. People in France exist, there is so much circumstantial evidence– at least some Frenchmen exist. You can feel that Frenchmen exist because of macaroon cookies and French music. We suspect Napoleon exists– he was well documented. We are pretty sure the Buddha exists, but even if he was a fiction character in a sutra, he’s exerting an influence on the collective consciousness of the modern living world. We are pretty sure the Bodhisattvas are ahistorical. And for that matter, Zeus, the Christian God, Brahma and Thor. And Harry Potter. But to the extent that these characters exist as role models and forces in the collective consciousness, they exist.
We can make them stop existing. Just stop thinking about them. We can will new ones into existence. Groups of people who don’t talk to each other, don’t share the same set of personages in the collective consciousness.
Anyhow, Buddhism is big. Any new comer must decide what texts they will accept. If they accept the Mahayana texts, they need to come to terms with the Bodhisattvas. The BNS only mentions Vairocana and the Buddhas of the 10 directions. So even if the foundational sutras are fictions and don’t exist as the sutras portray, not in a transcendent nor mundane way, we should pay attention to the Bodhisattvas. As long as we think about them, they live in our collective consciousness.