Or they're sending their personal regards in private, while publicly discussing the publicly relevant transition matters.
Just like what happens all the time when people quit things that happen offline. Not everyone feels comfortable or compelled to make such a statement in front of the team.
The individual stepping down says there are no issues with either of the other two leaders for the release. I'd have to dig, but it's likely a team of three to avoid ties and a have the responsibility spread out.
"Siding with the bullies" and holding up a release are likely unrelated.
Just like what happens all the time when people quit things that happen offline. Not everyone feels comfortable or compelled to make such a statement in front of the team.