Jesus said “There is no one good but God.”; we don’t have a good nature to discover. And good luck finding support in the new testament that getting baptism solves the sin problem.
Now if we are talking about a long long time ago, it’s more likely that maybe there was a bigger lack of information so that people could figure this out for themselves. In the end a lot of people just follow along with what one person days. Still quite common today however.