Board Thread:DC's Legends of Tomorrow discussions/@comment-807326-20171101020057/@comment-3221148-20171102214315

It's the topic of the show, obviously. If you want an in-universe explanation, let's say other shows happen after the Legends and Bureau fixed most of the anachronisms we see. After all, the whole point of the Bureau is that they were able to fix gigantic time warps with minimal effort and with erasing all public knowledge of the problem. So, maybe Oliver did see a giant dinosaur walking around Star City behind the scenes, but the Bureau agents came in, wiped his memory, took the dino away.

Not the first time we don't see the bigger parts of universe on screen. Remember that Eobard Thawne apparently had a whole DIFFERENT confrontation with the Legends that ended with Mick sending Rex Tyler with a ship and a message, a confrontation that Eobard wholly ERASED by killing Rex a little bit earlier.