Not easily, because it's closer to a convergence of smaller engineering decisions into an emergent choice to ship a CA bundle.
But the short version: lots of tools ship their own CA bundle. This is not ideal for distributors like Homebrew, because people expect one CA root program for the entire distribution. As a result, Homebrew tries (and sometimes fails) to apply a consistent root program across its tools. Apple's own roots are not inherently best suited for all Homebrew users, so we end up shipping a composite of their roots and the Mozila root program.
> What happens if they are in disagreement?
They are in disagreement, all the time! Root program operators are totally free to manage their trust roots as they please. The only forcing function is a desire to honor users' connections; differences in root programs end up getting papered over somewhat by cross-signing between different CAs.
Not easily, because it's closer to a convergence of smaller engineering decisions into an emergent choice to ship a CA bundle.
But the short version: lots of tools ship their own CA bundle. This is not ideal for distributors like Homebrew, because people expect one CA root program for the entire distribution. As a result, Homebrew tries (and sometimes fails) to apply a consistent root program across its tools. Apple's own roots are not inherently best suited for all Homebrew users, so we end up shipping a composite of their roots and the Mozila root program.
> What happens if they are in disagreement?
They are in disagreement, all the time! Root program operators are totally free to manage their trust roots as they please. The only forcing function is a desire to honor users' connections; differences in root programs end up getting papered over somewhat by cross-signing between different CAs.