Jesus thinks and studies for many years before He begins His ministry. There is a lesson there, isn’t there, about knowing your song well before singing? He had to get things right, and took care even though He was divine.
And regarding the Old Testament, it would be odd to have an extended and detailed historical narrative written by multiple authors over a long period of time, if it were all just a lie, would it not? What’s the point of a bunch of people who didn’t know each other sitting around in the desert over a a span of many centuries making up fake stories — often not particularly exciting stories — and painstakingly writing them down? The alternative explanation — that these people were writing what they believed to be God’s truth — makes more sense.