Ankylosaur was sluggish and deaf?

So German and Austrian scientists did a CT scan of the nodosaurid, Struthiosaurus austriacus and came to the conclusion that it's slow and hard of hearing. I don't think being slow is a surprise to anyone, but one would assume that even if it didn't have amazing hearing, having decent hearing would help it defend against what it can't see. Its eyes can only see so much. It still has blind spots. You would think its ears would help it detect what it can't see. It's a nodosaurid, so it has no tail club, but I assume once it detects predators, it would lower its body and let the armor do the protecting. What if it was ambushed?

I'm not doubting that its hearing's not great, I'm just baffled by how it survives despite the bad hearing. You would think it needs all of its senses to keep from being someone's lunch. Struthiosaurus austriacus isn't exactly a big dinosaur.