Russell was got up in the Adventist theology of the time influenced by ones such as publisher Nelson Barbour and at one time was the co-editor
of the Herald magazine. These two separated with conflicting ideologies concerning the return of Christ and his presence and Russell went
on his own publishing Zion's Watchtower.
I think there was impart some individualistic ego present which drove him to start his own published magazine contained with his own idealogical thoughts.
Maybe he thought that this could also resolve into a business opportunity as well, as its known both Barbour and Russell had business back grounds.
A bit of info about the two ...
As 1873 approached, various groups began advocating it as significant. Jonas Wendell led one, another centered on the magazine The Watchman's Cry and the rest were associated with Barbour. British Barbourites were represented by Elias H. Tuckett, a clergyman. Many gathered at Terry Island to await the return of Christ in late 1873. Barbour and others looked to the next year, which also proved disappointing.
Led by Benjamin Wallis Keith, an associate of Barbour's since 1867, the group adopted the belief in a two-stage, initially invisible presence. They believed that Christ had indeed come in 1874 and would soon become visible for judgments. Barbour started a magazine in the fall of 1873 to promote his views, calling it The Midnight Cry. It was first issued as a pamphlet, with no apparent expectation of becoming a periodical. He quickly changed the name to Herald of the Morning, issuing it monthly from January 1874.
Herald of the Morning, July 1878
showing Barbour as Editor
In December 1875, Charles Taze Russell, then a businessman from Allegheny, received a copy of Herald of the Morning. He met the principals in the Barbourite movement and arranged for Barbour to speak in Philadelphia in 1876. Barbour and Russell began their association, during which Barbour wrote the book Three Worlds (1877) and published a small booklet by Russell entitled Object and Manner of Our Lord’s Return. Beginning in 1878, they each wrote conflicting views on Ransom and Atonement doctrine. By May 3, 1879, Russell wrote that their "points of variance seem to me to be so fundamental and important that... I feel that our relationship should cease." In a May 22, 1879 letter to Barbour, Russell explicitly resigned: "Now I leave the 'Herald' with you. I withdraw entirely from it, asking nothing from you . . . Please announce in next No. of the 'Herald' the dissolution and withdraw my name [as assistant editor on the masthead]." In July 1879, Russell began publishing Zion's Watch Tower, the principal journal of the Bible Student movement. (Several years after Russell's death, the magazine became associated with Jehovah's Witnesses and was renamed The Watchtower.)
By 1883 Barbour abandoned belief in an invisible presence and returned to more standard Adventist doctrine. He had organized a small congregation in Rochester in 1873. At least by that year he left Adventism for Age-to-Come faith, a form of British Literalism. He changed the name of the congregation to Church of the Strangers. In later years the congregation associated with Mark Allen's Church of the Blessed Hope and called themselves Restitutionists. A photo of Nelson Barbour appeared in the Rochester Union and Advertiser in October 1895.
Barbour intermittently published Herald of the Morning until at least 1903, occasionally issuing statements critical of C. T. Russell. He wrote favorably though cautiously that he was persuaded 1896 was the date for Christ's visible return, an idea that had grown out of the Advent Christian Church. The last date set by Barbour for Christ's return was 1907.
So from Russell's history we can see that he was indeed caught up in adventist theology but he was also caught up in attracting the publics attention
from his own theological teachings, thinking how compelling they were, he decided to sell them to the public by giving public talks and producing his own literature.
But like all of these proselytizing religious charlatans past and present and even the ones before his time such a William Miller, publishing a book with these engaging
theological thoughts concerning the return of Christ were more based from emotion rather than strict adherence to the bible's writings and interpretations.
Those compelling instilled emotions which were originally created by Russell were exploited by the WTS. throughout the 20th century right up to this day
in the present JW religion.