Scanlan has been the least reluctant of all of them dating back to the second episode of season 1, when he had to be dragged through the tapestry to Brimscythe's lair. He also wanted to not fight the Briarwoods, saying they had evidence they could take back to Uriel. You are right in that they are emphasizing it here, though. Brimscythe did have a whole speech on how they used to rule the entire world.

All reactors struggle somewhat with the lore on this show, and I gather from watching the commentariat that we enjoy the opportunity to infodump. Don't sweat it

LET'S GO! :D (edit because I do actually want to comment more than just enthusiastic delight that you have reached season 2 :p) The dragons are... dragons. These are actually more nuanced than most, but they still suffer from a somewhat overwhelming history (Doyle-ian not Watson-ian) of being hoarders of anything and everything, with no real cause, and as such, they are a solid choice for villains that want to have power over everything. Think Smaug. The things they are taking aren't the point as much as the power and control. That said, these 4 (yes, 4. Acid, poison, fire, ice. They have names and titles but they are spoilery so I won't put them here. You will learn them when it's appropriate.) these 4 are definitely different characters with different motivations. The things they covet, and want to control, are distinct. The fact that they have formed an alliance at all, even when that "alliance" is more of a convenience, is remarkable, but the fact that the alliance is united under a single dragon?? That's the thing that makes it unprecedented. It wouldn't have been the first time that interests have overlapped, but following orders? Gilmore has good instincts, and this is bad. It's a lot of Lore(tm) but it's okay, everything you need to know IS covered in the show, as long as you're invested and hearing what's said. There are a few moments when things aren't as clear as they could be, because they're adapting hundreds of hours of ttrpg to 23 minute episodes, but nothing has been lost that you can't extrapolate. As you will have noticed, there will be an infodump from Critters (tm) ( myself included, heh, sorry not sorry) in comments, not because you're failing, but because we are a passionate bunch that wants to share. You can ignore all of us and still enjoy the show without knowing anything outside of the episodes

Don't worry about not getting everything right away! I don't know too much about DnD lore beyond what I've heard about in this show (which is supposed to be a more simplified version of what happened in the real campaign anyway) & what other comments have explained. And about Scanlan's fears about fighting the 4 dragons; he didn't show this same level of fear when fighting the younger Blue Dragon in S1 mostly because they were getting paid for it as a one-time deal, but he was still apprehensive. But now these are not only 4 dragons but ANCIENT ones that are working together, which is much more deadly. Especially in the eyes of a bard gnome like Scanlan who isn't really a warrior or fighter, unlike Pike who became more of a fighter rather than just a healer in S1.