And the reason is the last episode, the season finale. At least I believe it is the main reason, although I suspect quite a few people could not get past episodes 3/4. Which is a shame, as the series pick up from then onwards until espisode 7, which for me was the best, along with the intriguing opening episode.
So what is the issue with the season finale? I have written an extensive review of that episode, but to quickly sum I up (and also to have no spoilers, as there are quite a few in that one): it feels cheap. Like a low budget sci fi/horror mix, one that would go straight to TV. We have this great premise, this solid cast with some brilliant actors in it (I am a big fan of Rapace by the way, she is so underrated), some solid development...and you choose to go with characters doing the most illogical things and creating even further mess, along with stuff just...happening, to advance the plot, with no real explanation.
It is obvious this was destined for at least one more, if not numerous future seasons, but considering the ratings here, and no official confirmation from Apple, even though this TV series were close to the top of the rankings for some time, I am beginning to doubt those future seasons would happen. And I would hate that, as there is still hope for this, to turn out great. But it could have worked just as well, if not better, as limited TV series,8, 10, or even 12 episodes. Instead the creator decided to make the season finale a mindless filler not answering any questions, and creating new ones, including with the final scene, again completely unexplained and looking like it's there to be a final beg for renewal.