Chris Christie did not reinvent his campaign around dramatically heterodox policy positions; he largely ran as a conventional, anti‑Trump Republican and then suspended his 2024 presidential campaign on January 10, 2024 due to lack of a path to victory. (en.wikipedia.org)

What actually happened in the GOP race is that Donald Trump dominated from the start, while Ron DeSantis and then Nikki Haley were treated as the principal non‑Trump alternatives in polling and media coverage, with Vivek Ramaswamy generally in single digits. (en.wikipedia.org) In the first contest, the Iowa caucuses on January 15, 2024, Trump won in a landslide (~51%), DeSantis took second (~21%), Haley third (~19%), and Ramaswamy finished a distant fourth (~8%). (en.wikipedia.org) That night Ramaswamy suspended his campaign and endorsed Trump. (axios.com)

After Iowa, DeSantis suspended his campaign on January 21, 2024 and endorsed Trump, leaving Trump and Haley as the only remaining major candidates for the Republican nomination. (en.wikipedia.org) Haley then continued as Trump’s sole significant challenger until she suspended her campaign on March 6, 2024 following Super Tuesday, at which point Trump became the last major Republican candidate. (apnews.com)

At no point did the "effective contest" for the 2024 Republican nomination narrow to Donald Trump versus Vivek Ramaswamy. Instead, it effectively became Trump versus Haley (after DeSantis exited), with Ramaswamy already out of the race. Given that Christie did not make the kind of heterodox pivot envisioned and the race still did not become Trump vs. Vivek, Chamath’s conditional prediction is best judged as wrong.