Elderberry, JWs aren't the only ones who entertain the possibility that Michael could be Jesus. Here is a SDA article: https://www.adventistbiblicalresearch.org/materials/is-michael-another-name-for-jesus/
I'm pretty sure that I've heard Christadelphians refer to Jesus as Michael, which means that that is probably where Russell got the idea from. I also know of individual writers from mainstream Christianity who entertain the possibility. But it doesn't seem to be a tightly held doctrine in most denominations.