The Old Testament has so many prophets. How did they get their messages from God?

The answer surprises most people. The prophets received their prophetic messages in visions, and these visions often came during the prophet's sleep. For example, check 1 Chronicles 17:3, Isaiah 21:2, Jeremiah 31:26 (!), Lamentations 2:9, Hosea 12:10, Joel 2:28, Micah 3:6, and Acts 2:17-18. Moses was a conspicuous exception to this rule (Numbers 12:6).