To keep money streams and decision making for Firefox and Thunderbird separate?

So it can be spun off more easily?

Presumably MZLA is not a 501(c)(3) organization (a Delaware C Corp perhaps?) and can do things that a 501(c)(3) can't, even if the corporation (MZLA) is owned by the 501(c)(3) (Mozilla foundation, in this case).

Hopefully this doesn't mean we end up with pocket on our thunderbird home screens.

I came here to ask the same thing. What were the disadvantages of using the Mozilla Corporation? Will Thunderbird be the only offering in MZLA Technologies Corporation?