Becoming a seal requires you to be tough. It doesn't require you to be "good".
Don't ever trust that someone is "good" or "bad" simply because of their job title....
No but when you have bonded and been trained to trust a man with your life, it's natural to think you can trust him with $10,000 or $100,000. I can certainly understand why his fellow SEALs felt they should be able to trust him.