> When I started this project in January, gdb failed on every program I tried it on. delve didn’t work on OS X, and print-statement-debugging was too slow and limited. What's a developer to do? Make my own debugger, of course.

It seems like he tried to use delve and it wasn't portable at the time. Sure he could have worked on making delve portable instead, but he probably learned a lot more poking around the internals himself.