Not using Threads, but does anyone know if it requires a distinct new or account, or if you can login via your Instagram account? I'd imagine if the latter is the case, then this explain the high usage, if the barrier to entry is low (provided you already use Instagram). Also, I would be curious to see how many of the users remain active on the platform in the coming months.

You are able to use your existing instagram account. insta also puts a temporary badge on your profile with your sign-up number

You also cannot delete your Threads account without deleting your IG..

Only existing accounts work hence I can see a huge spike in users