What happened: In the 2024 U.S. presidential election on November 5, 2024, Donald Trump (Republican) ran against Kamala Harris (Democrat), not Joe Biden. Trump won with 312 electoral votes to Harris’s 226, and about 49.8% of the popular vote to Harris’s 48.3%.(en.wikipedia.org)

On “Democrats will lose”: This part is correct in a narrow sense: the Democratic ticket (Harris/Walz) lost the presidency to Trump/Vance.(en.wikipedia.org)

On “Joe Biden will be defeated”: This is wrong. Biden did not end up as the Democratic nominee; Harris was. Since Biden never faced Trump on the 2024 ballot, he could not be “demolished” or defeated in that election.(en.wikipedia.org)

On “by a large margin / demolished”: Trump’s national popular-vote margin over Harris was about 1.5 percentage points, the narrowest popular-vote gap since 2000, and the decisive states collectively turned on roughly 230,000 votes across Michigan, Pennsylvania, and Wisconsin—evidence of a close race, not a blowout.(cookpolitical.com) While Trump’s 312–226 Electoral College margin is larger than in some recent elections, major analyses characterize his popular-vote win as modest and historically tight.(cookpolitical.com)

Because the prediction specifically asserted that Joe Biden himself would be the candidate and would get “demolished” (a large-margin defeat), and neither of those key elements occurred—even though Democrats did lose overall—the prediction is best scored as wrong.