True, there isn't a single scripture that says Jesus is also known as Michael.
Why do many trinitarian scholars also teach this?
Why did many of the 1st century writers also teach this?
Matthew Henry's Commentary states:
"Christ is that great prince, for he is the prince of the kings of the earth," (Dan 12:1)
J. N. D. Kelly, in his Early Christian Doctrines, writes about the view of Hermas regarding the Son of God:
“In a number of passages we read of an angel who is superior to the six angels forming God’s inner council, and who is regularly described as ‘most venerable’, ‘holy’, and ‘glorious’. This angel is given the name of Michael, and the conclusion is difficult to escape that Hermas saw in him the Son of God and equated him with the archangel Michael.”
When did trinitarians stop teaching this simple truth?
When Jehovah's Witnesses started to used it to prove Jesus isn't God, but God's Son.