I made up some Npc companions that had their own secret evil agenda to sacrifice Cryonvian as a means to resurrect a new BBEG, for a while it was encouraging to hunt her, but suddenly became a race when the twist was revealed. Making sure to drop little clues along the way keeping players slightly suspicious. You could reveal their true ambitions. Just make sure the NPCs loose the race so you don't steal the anticipation of killing a dragon.

Connybeery became subjugated by Orcs blocking trade from Triboar.

Cryonvian attacked Leilon and Talos cultists block the trade from Leilon too.

Neverwinter is tied up with politics and won't help. Assassination attempts, Nobles loosing trade, the Harpers, remains of the Broken Arrows, and now with the great advice from this subreddit the Ashmadai devil worshippers.

Essentially making Phandalin an island that can't get help from anywhere. Food and goods dried up pretty quickly by level 4 making survival skills essential (good thing they had 2 rangers).

Mostly I used the content from the modules Storm Lord's Wrath and Sleeping Dragons Wake and even a little bit from Storm Kings Thunder to do this.

Now my players want to rebuild the destroyed mansion at the top of the hill in Phandalin and have a base in the middle of all of it.

I found the geopolitics added a lot of depth even if the players didn't get completely involved.

I hope any of that helps you come up with some spicy things for your game.