Chamath’s prediction was that by December 15, 2020, Trump would effectively be “out” and the post‑election contest would “all be done.” In reality, Trump’s efforts to contest and overturn the 2020 election continued well past that date.

Key evidence:

• A comprehensive timeline of efforts to overturn the 2020 election notes the main phase of attempts ran from November 4, 2020 through January 7, 2021, explicitly covering all of December and stretching into early January. (en.wikipedia.org)
• On December 21, 2020, Trump met at the White House with Rep. Mo Brooks, other members of Congress, and his legal team to strategize using the January 6 congressional certification to overturn the election results—planning that clearly post‑dates December 15. (en.wikipedia.org)
• On December 23, 2020, Trump personally called the chief investigator in the Georgia Secretary of State’s office, urging the official to “find” fraud, another direct attempt to alter certified results occurring after December 15. (en.wikipedia.org)
• On January 2, 2021, Trump held the now‑infamous hour‑long call with Georgia Secretary of State Brad Raffensperger, pressuring him to “find 11,780 votes” to overturn Biden’s win in Georgia—strong evidence that Trump was still actively contesting the election nearly three weeks after December 15. (en.wikipedia.org)

Because Trump’s legal, political, and behind‑the‑scenes efforts to overturn the election were ongoing and intensifying after December 15, 2020, the prediction that everything would be “done” and he’d be “out” by that date is incorrect.