KWED
Scratching head, scratching knee
But there is nothing in the historical biography of Bahaullah that shows he was a messenger of god. You only have his claims. And those claims have no evidence (or facts) to support them.They are the facts surrounding the Revelation of Baha'u'llah, the historical facts.
His Revelation is what He accomplished (His Mission on earth/ the history of His Cause)
That can be determined by reading about His mission in books such as the following:
God Passes By (1844-1944)
The Revelation of Bahá'u'lláh, Volumes 1-4, which cover the 40 years of His Mission, from 1853-1892.