This plays into the nature of the story of the drop, trying to take down a 'big bad.' The cards featured in the drop are all fantastic, and even the lowest-value card, Lightning Bolt, is a staple in every format it's legal in
Chrome Host Seedshark, in particular, could wreak massive havoc with the right setup
Y'shtola has a few things going on mechanically, and they all combine to make her a powerful Commander
Woodfall Primus is just good green value: a big, annoying creature with a strong enters ability that resists death via persist
They often target high-demand, high-dollar staples: Power 9, dual lands, Reserve List cards, and format-defining pieces
For that same reason, Ill also try to find space for Assemble the Entmoot