While he would never admit it out of simple modesty, Elrond considered himself the smartest person in his circle of acquaintances. Not to imply that all of them were stupid—quite the opposite, actually.
Gandalf was brilliant. A pragmatic strategist through and through. He was a bit on the impulsive side, however, and had an unfortunate tendency to think with his heart and not his head. But stupid? No, not by a long shot.
Thorin wasn't stupid either. He was nowhere near the same intellectual level as Gandalf, but he had a strange, indescribable charisma about him that made him a natural leader. And he was good at it, for the most part. But where Gandalf had a penchant for thinking with his heart, Thorin had a penchant for not thinking at all. The dwarf could devise an infallible battle plan on the spot with ease, but actually sticking to the plan and not doing something idiotic between point A and point B was practically impossible. Oh, and he was crazy as fuck, which didn't really help matters.
Balin was easily the most sensible of the group, but a bit too easily swayed by Thorin's spur-of-the-moment decisions for Elrond's liking. Well, to be fair, Thorin was the King, and Balin didn't really have much of a choice in the matter, but really. How hard was it to speak up and say "Hey, bad idea!" when Thorin's antics got out of hand?
Fíli and Kíli were a different story entirely. Both showed signs of intelligence that would develop somewhere down the road—Fíli more so than his younger brother—but for the present, they were morons. Sure, they were smart enough, but both seemed to have inherited the unfortunate trait of forgetting to think from their Uncle.
And then there was Bilbo. Bilbo was… naïve. Sheltered. In all fairness, the hobbit had never left the Shire in his life, so a bit of immaturity in the face of the rest of Middle Earth's problems was to be expected. And he caught on rather quickly, so Elrond really couldn't fault him for that. Now, the whole "I'm not afraid of Thorin" thing wasn't Bilbo's smartest move, and couldn't be chalked up to naïveté. But all things considered, Bilbo wasn't an idiot.
Which really left Elrond scratching his head at some of the antics of Gandalf and the Company. He hadn't been surprised when Thorin shrugged off his warning against entering Erebor, but Gandalf's dismissive shrug when reminded of the madness running through the line of Durin had been offsetting. Even getting the Council together to try and reason with him had been futile. Saruman was too entranced by the sound of his own voice, and Galadriel was too caught up in a game of psychic footsie with the Grey wizard to care.
In the end, Elrond was not in the least bit surprised to discover that he'd been right all along. Smaug had all but devastated Lake Town, deep-frying nearly half the inhabitants before being shish-kabobed by Bard the Bowman and flattening several more people as he fell to his death. Thorin had gone off the deep end and came frighteningly close to tossing Bilbo off the wall after deciding to go to war over a sparkly rock. Hundreds of Elves, Dwarves and Men were killed by two armies of Orcs that no one believed were coming until they literally came pouring out of the mountain. And, if the rumors were to be believed, a greasy little man with a unibrow managed to escape with all the gold in Dale stuffed into the bosom of his dress.
So, when the invitation arrived requesting Elrond's presence at Erebor for a big celebration, he wasted no time in packing his bags for the journey. Lindir seemed a bit surprised at how quickly Elrond had accepted, and was met with irritable muttering when he asked about it. "The Dwarves see the reclaiming of Erebor as a 'great victory' for their people," Elrond grumbled, "despite the fact that they did everything I advised against. It's a miracle the line of Durin still endures."
"It is fortunate Thranduil's Healers were able to be of assistance," Lindir agreed. "Though I can't imagine Thorin taking too kindly to being saved by an elf."
"Which is why I am so adamant on attending," Elrond replied. "If Thorin doesn't manage to offend the majority of Thranduil's party, those nephews of his will. Someone has to make sure they don't start another war."