So neither the Bab nor Baha'u'llah had any idea they were fulfilling Daniel's prophecy in Daniel 8? In fact nobody knew this until it was 'revealed' (oops, sorry, 'interpreted') by Abdu'l Baha in 1908! And he didn't get the idea from any Messianic Christian writings such as Miller's or those who followed him? Honest - he didn't!
We can see from the 'Terms' that Bahaullah used in His Writings, He made allusions that He and the Bab were fulfilling the Prophecies of Bible.
In the same Book, which you have looked a bit (Book of Certitude), you can see many of these allusions.
Let me give you one example:
it behooveth us to gird up the loins of endeavor, that haply, by the grace and bounty of God, we may enter the celestial City....
They that valiantly labor in quest of God’s will, when once they have renounced all else but Him,
will be so attached and wedded to that City that a moment’s separation from it would to them be unthinkable. They will hearken unto infallible proofs from the Hyacinth of that assembly, and receive the surest testimonies from the beauty of its Rose and the melody of its Nightingale. Once in about a thousand years shall this City be renewed and readorned.
Now in these paragraphs, what do you think Bahaullah means by 'City'?
He is referring to the Heavenly Jerusalem being renewed. Why?
He is referring to the Prophecies of the End, the Vision that John saw, the New Jerusalem coming down from Heaven. Abdulbaha explained this:
"We have before explained that what is most frequently meant by the Holy City, the Jerusalem of God, which is mentioned in the Holy Book, is the Law of God. It is compared sometimes to a bride, and sometimes to Jerusalem, and again to the new heaven and earth. So in chapter 21, verses 1, 2 and 3 of the Revelation of St. John, it is said: “And I saw a new heaven and a new earth: for the first heaven and the first earth were passed away; and there was no more sea. And I John saw the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband. And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and He will dwell with them, and they shall be His people, and God Himself shall be with them, and be their God.”
So, Bahaullah even when He was in Iraq, a major Muslim country, wrote that Book, in it, He is saying the Heavenly City is renewed, meaning the Prophecy is fulfilled.
Here is another example, Bahaullah pointing to OT prophecy, stating He is fulfilling it:
"Some lamented in their separation from Me, others endured hardships in My path, and still others laid down their lives for the sake of My Beauty, could ye but know it. Say: I, verily, have not sought to extol Mine own Self, but rather God Himself, were ye to judge fairly. Naught can be seen in Me except God and His Cause, could ye but perceive it.
I am the One Whom the tongue of Isaiah hath extolled, the One with Whose name both the Torah and the Evangel were adorned. Thus hath it been decreed in the Scriptures of thy Lord, the Most Merciful. He, verily, hath borne witness unto Me, as I bear witness unto Him. And God testifieth to the truth of My words."