In purely tautological terms, a criminal becomes a criminal by committing a crime or doing something that the law forbids.
From a variety of potential factors. Some of these factors may act alone but more commonly with a slew of other factors to create the perfect storm.
But the factors of the evolution of the criminal may include:
A list (not comprehensive)
Neurological dysfunction (tumors, neurological degeneration)
Childhood and familial history
'being in the presence of criminals is not the only way our environment can affect our behaviors. Research reveals that simply living in poverty increases our likelihood of being incarcerated. When we’re having trouble making ends meet, we’re under intense stress and more likely to resort to crime.'