Threads is Meta, one of the largest corporate enshitifiers on the internet - the crap most of us fled from that landed us in the fediverse in the first place.

...it's userbase is a relative ocean compared to the fediverse's drop, so the immediate concern is being able to moderate the tsunami of submissions; the long term concern is that things go peachy at first and the fediverse becomes so intertwined with Meta that it becomes functionally dependent on it... and then Meta decides to pull the plug, effectively destroying the parts of the fediverse that didn't defederate right out of the gate. This is called "EEE" or "embrace, extend, extinguish" as others have mentioned in this thread. It's a shitty thing bigger tech can do to destroy budding competition before it has a chance to become actual competition. Google has a history of it, and a lot of folks here naively think Meta will for some reason handle things more ethically.