The picture you stated is from 2019 is actually from 2018. For comparison here is a picture from 2019 along side your 2020 picture. As you can see the progress is not as drastic, and could easily be achieved under direction of professional nutritionists and physical trainers. The transformation you claimed took 'one month' was actually two years.The thing is also that a very specific method has to be developed to detect doping compounds. And in the compunds themselves you don't have to change a lot to make them undetectable for these methods. In some cases just a adding a methyl group to an anabolic steroid makes it undetectable for assays that would have caught the unaltered steroid.
Also, they have a lot of clever people who can set up a nice testosterone cycle that significantly boosts performance without reaching threshold levels for detection.
A very famous case for this is FC Bayern's Leon Goretzka:
On the left is Leon in May 2019. On the right is Leon in May 2020. The transformation took place during a one-month (!) Covid break. Here's a trained athlete who just out of nowhere puts on ginormous amounts of bulk in his mid twenties in an insanely short time period. No positive doping test turns up. They are always one or two steps ahead.
Edit: Of course, other Bayern players bulked up as well. They won the Champion's League that season...
COYB!
John.
