Act as if you love someone - to gain love
Becoming Religious is like marrying G-d- don't just hope she's right, examine her and see if she seems good, then marry her - but you still aren't sure , only maybe 98% sure, that is Emuna.
If the Commands are made up, people in the past wouldn't have accepted some laws which are senseless., shmita, kashrus.
If you go to tribes to sell them the stories - they wouldn't accept it either because it criticises their ancestors, Yehuda nad Levy for example. Killed (or tried to) Joseph. Even Moshes - the ideal man- was without faith in G-d - He hit the stone to get water. The writers would not be looking to insert flaws in the main characters.
Historical psychological genious(hidden codes) proofs.
We ask questions , we look for contradictions , and we find answers If the book were flawed, we'd destroy the Torah - it would fall apart - it would be answerless. Book is so full of moral ideas- it establishes an absolute moral. Movements like Communism try to make the world a better place, Judaism says , start by self help, make people better. That will fix the world. Equality - people do share some traits, we are all in image of G-d, we all have free choice.
Why not just be a good person? What is good? You need a moral system for evaluating behaviour- not just doing good. Should man or G-d decide good vs. evil- Man determines good by his current mind set/behaviour. Behaviour is the determinate - not the moral which follows the behaviour. Morality vs. self interest. Everything is good if good is what I am doing or What is generally done or what you are doing.
Jewish good leads to greater life, achieving a meaningful life (In the western world that is just being a financial success).