The Hobbit: Why Didn't Gandalf Defeat Smaug Like He Defeated The Balrog 60 Years Later?

gamerant.com:

Everyone who has seen the Lord of the Rings or The Hobbit trilogy knows that Gandalf is an unstoppable figure. He manages to persuade two of the most stubborn men in Middle Earth (the sick and poisoned mind of King Theoden of Rohan, and the paranoid and delusional Steward of Gondor Denethor) to let him intervene in their affairs, even when all of the treachery and darkness around them told them not to. Across both sets of books, Gandalf battles many enemies, slays many orcs, protects (and sadly loses) many friends, and he is the instigator of the two quests which, each in their own way, determine the fate of the entire world and all of its people.

This is even more impressive in The Hobbit and the Fellowship of the Ring than it is in the Two Towers and the Return of the King, because in these earlier stories he is still Gandalf the gray. Even at this point, before he has come into the most powerful version of himself, he is capable of great good, but also great evil, and holds the future of the world in his hands. During the famous battle against the Balrog in Moria, Gandalf manages to save his friends by distracting the beast, and breaking the bridge of Khazad-Dum so that the creature cannot follow the others. He gives his life to defend his companions, and he manages to beat this massive force of darkness and dread. This has led many fans to question why Gandalf didn’t simply go into the halls of Erebor during Bilbo’s quest 60 years earlier and get rid of the dragon himself?

Is Thranduil More Powerful Than Elrond?

If the whole point of the mission to reclaim the lonely mountain was a political strategy to fortify the north and prevent the Necromancer (who is later revealed to be Sauron) from using the dragon against his