Probably because the media knew he was on PEDs but couldn't actually say anything due to NDAs or something shizz.
Hard to say, he's always had hot and cold performances. I don't think, realistically, you can pinpoint any one thing and say 'that's the reason for his decline ' - it could be injuries, it could be lifestyle, it could be a lack of top level fights keeping him sharp. Perhaps all of those factors. But I don't think any fighter - even at heavyweight - can be at their best in their mid to late 30s. I think he probably has declined, but still looked good in his losing efforts against Usyk. But I don't believe his decline means at all that a prime Fury beats a prime Usyk.
Fury’s elbows and and ankles are shot but so is Usyk’s back and shoulder by all accounts. However the lifestyle of each fighter are chalk and cheese.
Sure, but if that triggered his decline then the real issue there is with sensitive flower Tyson for letting this get to him. Same with the elbows, which are likely a result of bad lifestyle, extreme weight fluctuations etc. that put strain on the body. Ultimately, Tyson could've been more (though he achieved plenty), but he lacked the key boxing attribute of discipline. Ironic that he'd often play the cheesy 'Spartan' gimmick when his lifestyle was anything but. The mental health stuff I have more sympathy for, but ultimately it's hard to tell where that started and the poor discipline ended.