Its sad that there are people here that need this explained. They dont understand the levels to this shit.
You need to understand that MMA fighters, especially in UFC, are different kind of humans. Just because you are packing 290lbs of pure muscle and you are 6.2, doesnt mean you can beat smaller guys like Aldo or Yan. Aldo kicks your giant leg, you go down and weep in pain. Yan lands one liver punch, you fold like a chair in excruciating pain. Or they can simply dance around you while you hit air until you are dead from exhaustion.
We are not even talking about UFC HWs. Big Frank can literally kill you if he lands with full power. The scary part about the fighters is that they retain these skills, power, and endurance even later in life. Sure they diminish with age, but whats left is still much higher than what your average Joe has.
If you think that 25 years old roided bodybuilder can beat 56 year old Tank Abbott, you are in for rude awakening.