It's long, it's rambling, it uses phrases like "laser-focussed" (twice). Fine, it's not corporatese at its absolute worst (there isn't a "synergistic" in there), but it's also not going to win any awards for clear communication; it could be every bit as diplomatic whilst also losing about 70% of the words.
Many inside of Mozilla, including an overwhelming majority of our
leadership, feel the need to be laser-focused on activities like Firefox
that can have an industry-wide impact. With all due respect to
Thunderbird and the Thunderbird community, we have been clear for years
that we do not view Thunderbird as having this sort of potential.
However, as I say, it’s clear to me today that continuing to live
with these competing demands given our focus on industry impact is
increasingly unstable.
So, their stated goal is market dominance for Firefox, period. Nothing else really matters. Clearly they are failing at this goal, so they are focusing their resources on it and discarding anything else.
I hope this isn't the end for Thunderbird.