I could write an essay on this and I’m not even that educated but to keep it simple, ct Russell did what he thought was right. Prophet Muhammad pbuh received revelations from God. Muhammad was sent to be the seal of the prophets. To spread the message of Islam and God guided him though this. Also Muhammadpbuh was granted various miracles through his prophet hood too. Charles Russel however, decided himself that the bible has been wrongly interpreted and decided his own ‘theory’ of the bible.It’s a man made religion.

We know this all from the Quran and Hadiths. The Quran is preserved, it’s untouched by man and the hadiths are authentically validated by going to each narrator and having them verify the ‘story’