The keyword here is suspension of disbelief. Storm King’s Thunder starts out in a very linear fashion with a series of events befalling a fortified village. Within one week the village gets bombarded from the air by giants in a floating castle, then the residents move out and find shelter in a bat cave where they get captured by goblins, the goblins start looting the village, the adventurers arrive and start killing the goblins, then the Zhentarim (a semi-evil political faction) try to take over the empty village, and then a horde of orcs attacks. (In the videos the DM replaced the orcs by more Zhentarim, but added an deus-ex-machina dragon saving the village). So the adventure for the group consists of searching through the abandoned village and killing the goblins, then beating back the Zhentarim, then beating back the orcs, and then finally going to the bat cave and freeing the kidnapped villagers. Then the villagers send them to another town very far away for rather flimsy reasons, and there the adventure loops backs to the giants. As far as stories in D&D adventures go, this is one of the less believable ones. But of course if you don’t care and just enjoy the ride, a lot of fun can be had.
It reminds me a bit of MMORPGs, where the story can also be rather weak, but is basically just an excuse to lead people to gameplay. In the D&D videos the story leads not just to gameplay in the form of combat, but also to fun situations where the DM describes a situation in more detail and the players come up with all sorts of plans and ideas instead of just rolling for initiative. A good group and a good DM are the ones where the players constantly fire off ideas, and the DM rolls with them. Then the actual story of the adventure becomes a less important backdrop, because the important story is the one that evolves from the players being in unusual situations. The art as a DM is to get people to play that way. I’m working on that.