Your ex was not completely truthful. Birds of a feather flock together. I have no idea why one turns to drugs. I believe with my daughter she started sneaking smokes in 5th grade, graduated to pot in high school and that led to crack and that led to heroin. She had to be number one and I think in one of my stories I explained her downfall.

https://medium.com/@hklarajane/my-daughters-messed-up-now-but-she-wasnt-always-that-way-ac1628b07a2e