Reminds me of those old disruption tactics

Who would the fifth column be working for in this case? Guix?

just seems like extremely poor communication and more "open letter" bullshit that's really a nothing burger. Seems like one or two people said "we're disbanding!" while based on some threads I've read the remaining team was like "yeah...we really didn't want to"

There is no remaining team. The two people who are resigning here are the entire team (originally it was four members, but two had already resigned previously). What's the point of having a team without any members?

just privately quietly resign

How are you supposed to "quietly and privately" resign from a community project that versions team membership and responsibility in Git? Genuinely, what are you imagining that is lower profile than this and not wildly irresponsible?

To be clear, they tried to keep the team alive. Originally it was 4 people. Due to the amount of pressure "from below" (as in, lots of requests to decide on how to do something in Nixpkgs, with whatever decision the team makes stirring up controversy) and the lack of communication "from above" (as in, the difficulty in figuring out the boundaries of their authority with the steering committee) two people burned out quite soon. The remaining two issued a public call for more volunteers and even reached out to people directly, but only one person was interested and AFAIU they did not end up joining the team.

Now, finally, both of the remaining members burned out, and with noone stepping up after repeated calls for new volunteers, the team has no other choice but to disband. No reason to keep a team that's literally empty.

As for their open letter, I think it was well-written and not combative or performative in any way. They pretty much just announce they are disbanding, explain the reasons why without putting any blame on any individuals, and thank everyone for their help.

I feel like the effect of the social media zeitgeist has turned a lot of people, especially those born in this century, into permanent performers. That's not to say that their actions are purely performative, rather that to them if it doesn't happen in view of the entire internet then it may as well have not happened at all.