It was like that because before we have decent enough infrastructure, distributed networking was really inefficient. Like early days of BBS/usenet, it’s like heavy copy&paste labour to move content from one server to another(until the protocol improved), then we have www that makes everything easier, then forum as news aggregator, then search engine, etc. Like hosting huge amount of data isn’t really easy to do or can be accessed from almost anywhere. Even lemmy/fediverse could have it’s down side in terms of discovery, ease to search, migration and for example accountability(DMCA take down can still be a thing if somehow a community is hosting copyrighted contents).

But I agree, with modern tools, we shouldn’t rely on any corporation, even non-profit org(cause they can always be sold and become for profit) to host community driven contents. Any niche community that value their own data should already looking for alternatives after this event. Like reddit can still be a place of portal to redirect traffic, but valuable information and sharing should still be on community owned server where everyone can backup. (ie. many game community have reddit sub that directs people to their own discord server, while still owned by a corp. the niche community on reddit can do the same and direct their subscribers to a new server they can operate in peace. )