But according to Andrew Kelly, Bun was full of bad Zig practices. So why did they keep pushing forward with Zig?
Because their ego got hurt that a big project decided to not use their "amazing" language.
It seems you misunderstand what happened to Bun: Anthropic has burned some investor money for a PR stunt -- our LLM can port this -- and also to punish Zig which dared to ban LLM contributions by taking away a significant project from the ecosystem. It worked, Rust didn't dare to enact a similar ban.
Indeed it's surprising, given the zig compiler famously causes all developers who use it to merge into a single organism with a combined nervous system.