The basic idea behind bootstrappable builds is to create a system that can be built without relying on pre-built artifacts. ""Can we go from zero to the modern day without having to just assume the existence of these already-built-for-us artifacts?"" The classic recipe for yogurt requires some yogurt to start the process, which is like how we normally build a C compiler today—we start with an existing C compiler binary. You might think about making sourdough bread with your grandmother's starter brought over from the old country; ""we're basically making C compilers with Dennis Ritchie's starter carried over from Bell Labs"".