I think many people will agree with me when I say the final part can make much more sense

Ok so getting straight to the point - Leo definitely does not give 2 fucks at all about a ‘drug free’ environment. BUT the connection can make much more sense in 2 or more ways-

1. With das & co being demolished and most probably all the drugs are gone aswell. Maybe in an attempt to be back in business after the factory was initially burned 1999, they somehow got stuck under rolex who’s ofcourse not happy that another batch of his drugs are gone,so he’ll prolly start tracking the culprit,leo and all because of that leo decides to join vikram and the boys.

2.leo and rolex could somehow have bad blood from the past and leo could find out that joining vikram could mean he could get his revenge or something on Rolex,so he joins him just for that.