IIRC other instances have made the same choice with these two instances. Mods and admins are small teams of volunteers, if one instance's users are creating a disproportionate amount of work for mods/admins I don't blame them for defeterating.
Do you have any sources/evidence of that? I went over there a bit after the first wave of defederation hullabaloo and generally found the tankie ratio to be roughly the same as anywhere else (extant but uncommon)… I didn’t see any rampant pro-CCP propaganda, either, as I’ve seen repeatedly claimed.
I have to wonder what the true story is, because the tankie/authoritarian narrative being circulated doesn’t actually seem to be true.
There's an image macro on hexbear right now about Chinese farmers being coerced into farming for China's food security rather than things that are profitable. The people on hexbear are 100% in favor of that. If you read the article though, it says that one of the goals of the CCP is to lift farmers out of poverty, and forcing them to abandon profitbale crops in favor of food security for the country is pushing them right back into poverty. Again, the general commentors on hexbear don't see a problem with the state forcing farmers into poverty to meet the needs of the state. That's a very pro-authoritarian (e.g. tankie) view. They're ignoring the harms, and the heavy-handedness of the CCP, while saying that it would be a dream to work in the fields instead of working in an office cube.
So, I dunno what to tell you. If you're missing the authoritarian narrative, it's because you're not looking.
And those instances certainly does that. Take a look at the meta thread in lemm.ee proposing defederation from hexbear, where hexbear shows up in brigade proving the point of the request and causing the thread to be locked by brigading and shitposting.
Same shit went on in other instances when people proposed defederation from hexbear, hexbear users flooding the threads and brigading the hell out of them, which is problematic systematic behaviour on its own, but especially so when the victims are smaller instances with only few users.