A Shadow Out of Time

The Crossing
S01E02
Season 1 Episode 2

I'm glad the sheriff started to put his son ahead of the apex & her daughter.

So Leah is a common & has the disease. That's dumb, I was hoping when they showed the black market apex doctor that he had a cure for Mantel's disease. That would make the show much more interesting. Instead they are keeping the disease at bay using apex blood. Stupid.

I thought the other time travelers were apex, but instead they are commons. That's good. Like Travelers, they've been trying to change the future but it sounds like they haven't prevented the creation of biotics, I mean apex.

How did the commons create time travel but the super-smart apex did not?