Because he was still young and he is talented fighter, but PEDs gave him edge in very important fights - he was caught several times, no doubt about that. Especially when it mattered the most (DC rematch he was caught twice)
He left LHW at the early age of 32, after those 2 very close fights (Reyes fight he possibly lost). That was when he started to fight fighters his age (outside of Gus before)
Stipe/Gane are ok wins, but not much more. Gane is complete amateur in wrestling - Stipe tough and pure warrior but way old and past prime - also he had swollen knee (check weigh ins), and limp was noticeable in pre fight videos, his movement was not that great at all.
It gave him an edge in the fight it was ruled a NC, I.e, vs DC 2. Curiosity, DC in his interviews always nightlight JJ talent, saying he didn't need that to win. Gus said the same thing. It'd be weird for DC to focus on JJ's talent if he truly believed only JJ had that secret. Chael form example, when Ariel asked if JJ was clean vs him, answered "no, of course not... Ariel, we know our own. I had more juice than a full Tropicana and yet he pushed me around the cage like a bear" ... Chael admitted he was, he assumed JJ was.
His only NC fight was vs DC 2, hence, only that one. The times he was caught, the fight was cancelled, hence, he didn't fight. Duhh.
Also, steroids fuck ppl over longtime. It boosts performance but athletes can't keep peak for a long time if they over did it. Yet JJ looks prime and Stipe who's 4 years older than JJ, is faced like current Tyson... I mean, steroids age the athlete a lot. If JJ doesn't age to the point that at 38, fighting a 42 Stipe was looked like "dragging a geriatric to fight", then his chemistry knowledge is GOATED as he developed chemicals who not only doesn't age him, but makes him peak Jones ...
No, Stipe was very good. See the analysis data driven... His reaction time was comparable to the Stipe who fought Ngannou the first time. It only dropped after the insane punishment he took. And Tom when reviewing the fight, once the UK journalist said "yeah, but Stipe was 42", replied "no, actually, Stipe didn't look old ... After 30 elbows on top position for Jon Jones, the fact he still could keep the pace until the last spinning kick was surprising to me, that tells me his condition was way better than what one would expect. Which goes in hand with Stipe saying the lay off was better due to recovery and he could focus everything in a fight de himself deemed as "one he has always wished"...
Btw, JJ will fight Tom. He agreed to the fight, it's just a matter of when they release it... If JJ beats Tom, then ppl here are gonna make a ruckus of everything