Wanting to own billions isn’t necessarily evil. I’d say it’s actually pretty common to want to be a billionaire in our society; the desire to gain wealth is core to capitalism. They may not understand the consequences of it or be able to conceptualize of the people they’d hurt.
Hypothetically, if we treated it as an illness (or rather a symptom) we could shift societal norms and rehabilitate people who express signs of trying to hoard wealth.
This is a myth; the term “bug” for mistake predates the famous moth incident.