What were they thinking?

[Maédhros]

Perhaps they had hopes (still pipe-dreams, mind you, though perhaps not quite as impractical as they might seem at first glance) of burglaring some of that quality Erebor armor and lucking into a few battle-masks and going toe-to-toe with the old wyrm.

Could be but I mean, the dwarves couldn't beat the spiders in the forest of Mirkwood, how could they hope to slay a dragon?
Again, who knows what they were thinking?