The strains of marijuana thought to be new and higher potency have been available for decades, at least as long as I was a college student in the late 70s.
It had names like Thai stick and sensimilla.
And you can thank our friends in the DEA and their paraquat spraying for taking the growing indoors where the environment is much more easily controlled.
Thai stick was nothing more than somewhat-decent pot sprayed with a little hash oil, and while the sinsemilla of the time was good, they've had 40 years to selectively breed the best lines into the highest THC content.
The stuff that's around today is markedly stronger than in our time.