I do not consider them the "main evidence" because Baha'u'llah did not point to them as the evidence that supports His claims, but they might be considered good evidence for some people who put a lot of trust in the Bible. Some people say the prophecies are too vague to be useful, but that is not the case with all the prophecies, as some of them are very specific. Taken as a whole, I believe they are proof that Baha'u'llah was the return of Christ and the Messiah of the latter days, and I was never even a Christian.
Yes, that is what Baha'u'llah wrote regarding the evidence that establishes the truth of His claims.
“Say: The first and foremost testimony establishing His truth is His own Self. Next to this testimony is His Revelation. For whoso faileth to recognize either the one or the other He hath established the words He hath revealed as proof of His reality and truth. This is, verily, an evidence of His tender mercy unto men. He hath endowed every soul with the capacity to recognize the signs of God. How could He, otherwise, have fulfilled His testimony unto men, if ye be of them that ponder His Cause in their hearts. He will never deal unjustly with any one, neither will He task a soul beyond its power. He, verily, is the Compassionate, the All-Merciful.” Gleanings From the Writings of Bahá’u’lláh, pp. 105-106
Certain atheists will disagree with me, but I do not think an ordinary man could have achieved what Baha'ullah achieved on His mission, nor do I think an ordinary man could have written the 15,000 tablets that He wrote.
God Passes By is a historical account of the mission of Baha'u'llah from 1853-1892.
Below is an excerpt from one chapter:
“So prolific was this period, that during the first two years after His return from His retirement, according to the testimony of Nabíl, who was at that time living in Ba
ghdád, the unrecorded verses that streamed from His lips averaged, in a single day and night, the equivalent of the Qur’án! As to those verses which He either dictated or wrote Himself, their number was no less remarkable than either the wealth of material they contained, or the diversity of subjects to which they referred........
A certain Muḥammad Karím, a native of
Shíráz, who had been a witness to the rapidity and the manner in which the Báb had penned the verses with which He was inspired, has left the following testimony to posterity, after attaining, during those days, the presence of Bahá’u’lláh, and beholding with his own eyes what he himself had considered to be the only proof of the mission of the Promised One: “I bear witness that the verses revealed by Bahá’u’lláh were superior, in the rapidity with which they were penned, in the ease with which they flowed, in their lucidity, their profundity and sweetness to those which I, myself saw pour from the pen of the Báb when in His presence.
Had Bahá’u’lláh no other claim to greatness, this were sufficient, in the eyes of the world and its people, that He produced such verses as have streamed this day from His pen.”
God Passes By. pp. 137-138