posts and comments are hosted on the instances their authors come from. if the instance hosting a community gets yanked away without sending proper deletion requests to the network, all those posts end up hidden but accessible with their "canonical" link (which you can find from the rainbow star looking button on each post)

for example, the canonical link to OP's post is https://sh.itjust.works/post/2882678, and if db0 goes down without asking shitjustworks to remove this post (i.e. if it gets seized) that post will stay there until the sijw admins or OP themselves takes it down

(and if an instance does get seized other piracy-friendly instances can immediately defederate from that instance to "reject" any future removal requests wink wink nudge nudge)