Jarred didn't port esbuild, his vision/ambition is far beyond that for bun. But even as a transpiler, Jarred made different decisions about the compilation process. Also time doesn't really mean the same thing, this brosef works 80hrs/week on this stuff, and he's been doing that for over a year.

He chose Zig because it's a good language for performance sensitive applications and found himself to be very productive in it.