Not having seen The Iron Fist, I didn't get the whole plot line about his fist opening some gate. What was it, a monster machine? A creature? Why bring down NY? How was destroying the city going to get the members of the The Hand home?
I would have given the series a much higher rating if it weren't for this confusing plot.
There were dragon bones down there. The dragon bones were the source of the until-then-mysterious 'substance' the Hand elders were using to maintain their immortality and resurrect each other (and their choice flunkies), which they stole from K'un-Lun (from which they were expelled for these necromantic experiments in the first place).
Some previous Iron Fist or Fists had travelled the world sealing away any other sources of the dragon-bone-immortality/resurrection substance, to keep them from exploiting it.
It was pretty basic. They wanted to live forever, and have a ready supply of the magic substance they needed to cheat death over and over.
How exactly mining the dragon bones would cause New York to collapse, I have no idea. That's where they lost me. Does the mystical energy of the bones somehow reinforce the ground around it? Wouldn't Dr. Strange be likely to know if New York was held up by magical energies from deep beneath the ground? Eh. I'm not even going to try to make sense of that part. The Hand elders getting access to an unlimited supply of their immortality/resurrection substance, able to not only keep themselves immortal, but use willy-nilly on their favorite minions (like Nabu) is more than enough threat without the earthquake business, which, IMO, was a needless addition to try and ratchet up the tension.
I was very impressed with the tying together of the Hand with K'un-Lun, with the dragon bones / 'substance' as connective tissue. It was a neat way to at least bring Matt and Danny's stories together.
I would like for season 2 to perhaps tug on connective threads tying Matt and Jessica together instead (the chemical company responsible for blinding one and empowering the other), and perhaps tying them into other chemical-empowerment threads, like the mysterious chemicals used to empower Luke Cage, or the pills used by 'Nuke' and later Trish to gain temporary super-powers. Is there a 'Power Broker' working behind the scenes in New York, working to produce metahuman enforcers for entities both quasi-legitimate (the special forces that Sgt. Will 'Nuke' Simpson worked for) and illicit (criminal elements)? It would be more of a challenge for Luke, in particular, to face enforcers for that company with bulletproof skin like his own, and strength to match, and be far more of a challenge for everyone else than 'yet more ninja.' Less Hand and ninja. Less focus on Danny, who seems to be the weak link, actor-wise. (Although he could also be connected, if Rand Enterprises has a connection to the chemical company in question, or Rand resources can be leveraged into fighting them on a corporate front, while the team punches face at the street level...)