I still prefer the original short story, where George is just a lowly bank clerk. He does nothing in particularly important (Capra took the concept of a banker who lends on the character of his customers, and they come through when he’s in a financial jam, from American Madness, which he directed from Richard Rossen’s script). But by merely going about his mundane job, he made a big difference to the town.
In the story, he beat out another guy for the job. In the “never been born” timeline, that guy embezzled funds and caused the bank to fail, ruining its depositors and wrecking the town’s economy.