Scholars like Brown and EB Elliott back in the 1820s held that it was Nebuchadnezzar's ascension year that started the seven times. They thought it was 604-1917 or 606-1914, but it was not based on Jerusalem's destruction as that was 587.
Back then they looked to the 6000 years as ending in the 1870s. Nelson Barbour felt that the current belief that it was 587BC meant that the desolation was 50 years from 537 to 587. In March 1874, in the Midnight Cry, Barbour combined the two periods of captivity and desolation into one. He changed Jerusalem's destruction to 607 and Russell followed that. When Russell split from him, he should have examined his chronology too.
I adhere to what Elliott taught, that the seven times ran from around 606/604 to 1914/1917 and was not connected to the destruction of Jerusalem.
So blame it on Nelson Barbour who changed history and Russell and his followers for adhering to it.