USADA isn’t real, they were just brought in as a smokescreen to help sell UFC to the mainstream, they’re paid in house by Dana who calls the shots.
But for the sake of argument let’s pretend for a second that there was real drug testing.. if you know anything about steroids it takes a lot longer than 6 months to lose the benefits, and studies showed test usage has some permanent benefits to strength. You still have the majority of the gains for years after a cycle, hence what Conrad is doing is cheating.