Thorin Oakenshield's decisions in 'The Hobbit' ripple outward in ways that affect the later events of the War of the Ring, though it's often indirect. His reclamation of Erebor doesn't just create a dwarven homeland; it re-establishes a major power in the north that draws Sauron's attention. More crucially, it puts the Arkenstone and a massive dragon-hoard back into play, which I think fundamentally alters the strategic landscape. Sauron, already seeking the One Ring, now has to consider a rich, refortified mountain kingdom as a potential ally or enemy. The Fellowship benefits later because Thorin’s actions—and his death—leave Dáin Ironfoot as a steadfast ally. Without that reclaimed kingdom, the forces at the Battle of Dale and the Siege of Erebor during the War of the Ring simply wouldn’t exist to tie down a huge chunk of Sauron’s eastern armies.
But the personal impact is subtler. His handling of the treasure and the dispute with Bard creates a legacy of diplomacy and debt. Bard refounds Dale, and the Men of Dale and the Dwarves of Erebor become key allies for Gondor and Rohan. If Thorin had been less stubborn, maybe that alliance forms smoother; if he’d been more diplomatic, maybe it’s stronger. His initial greed and subsequent sacrifice sort of set the tone—a flawed hero whose choices show that reclaiming a homeland isn’t just a military act, but a political one that has to be paid for. That debt, literally and figuratively, gets paid by his kin later, which secures the northern front and allows the Fellowship’s quest in the south to have a chance. In a way, Thorin’s tragic arc cleanses the dwarves’ legacy from the dragon-sickness, making them reliable partners when the real war comes.