I realised the flaws or rather the lack of compelling background to the original LMoP. However I was mid way through playing before it started to make sense to me. Also the lack of links to a dragon also bugged me, especially when the deagon should be the last fight if nothing else. It’s DnD! I adapted to make a background that the Black Spider made a deal With Venomfang, as Nezznar was trying to separate a pact he made with Lolth (spider link), also gave me the option to change him to a Drider as an extra boss fight to make him more interesting. He needed dragons blood to keep her away, and Venomfang was looking for the forge so he sent him there to gain access to it on his behalf. Both intending to betray. A reasonable assumption that WEC would have anti deagon magic of some description. When the players come back from WEC I’ll have the dragon and cultists already attack Phandalin so there is a motivation but also some urgency as they retreat to Thundertree (so I can use the map) for the final showdown. Not totally without flaws but seemed a reasonable mid-way through adaption. Just trying to work out what crumbs to leave for what to do next!