I’m not really understanding why you’d need to convince anyone of anything? Why would you need to tell anyone you went back in time? All you need to do to become rich when going back in time is to memorize a winning lotto ticket or to invest in something that you know will make it big. Why do you think that you’d need to convince people you aren’t crazy or whatever you’re saying? Legitimately curious.
With going back and time, you could both become rich and change things and events from your past that you regret.