How the hell can a stegosaurus outrun an allosaurus?

I was on the cusp of becoming an adult allosaurus. Over 40KPH as a pretty agile predator, I thought I was nimble enough to at least outrun big herbivores. But no, two big fat stegosauruses homed in on me and turned into prime Usain Bolt, beat the shit out of me and relentlessly chased me down until I bled out. We seemed roughly equal speed, but they were quicker. I thought I could outrun their stamina but they just kept running for ages.

Why the fuck can't a teenage allo outrun a lumbering stegosaurus? In real life it's predicted that allosaurus could run up to twice as fast.

I just checked the speeds of each dino on one of the information websites and apparently sub-adult allo can get around 41kph, and stego gets around 26kph. I was on a well-rated server (Isla Paradisa) so I doubt it was cheating? How come they could outrun me and were able to hit me until I died while I was at full sprint?