It is in the numbers. Dricus is a former K-1 kickboxing champion with a 32-0 record. He has had belts in 3 different organizations and 2 different weight classes. In UFC, he has finished every opponent except Strickland and Tavares. Strickland's nose was broken in the 2nd fight, but he refused to give up. Started running instead with Dricus running after him.
He also was finishing his opponent with only 13% Oxygen through his nose before the Whittaker fight when he got his nose fixed. Now, he is a cardio machine who goes 5 rounds pedal to the metal.
As far as strength, just ask the people who have actually fought or trained with him. RDR, Luke Rockhold or Whittaker. There is a video of 260 lbs Aspinall and Dricus in a clinch. Aspinall could not overpower Dricus in the clinch. Whittaker said when Dricus just popped up after he took him down. There was nothing he could do to hold him down. He said he did not realize how strong Dricus was until he could not hold him down.
Also, Dricus hip tossed Whittaker, which is very difficult to do on a person who weighs around 195 - 200 lbs.