Facebook the product is still Facebook. The only name that changed was that of the company that owns Facebook, which makes sense as that holding company also runs other products like Instagram.
Google made a similar move in 2015 when it created Alphabet to hold the non Google parts of Google.
In both cases the renaming was on the coorporate side. They made no effort to loose the old trademark, and continue to operate under it today.
The only high profile case that comes to mind that is simmilar to Twitter is when Comcast rebranded itself as Xfinity in 2010. In that case, it worked because: A) Comcasts reputation was way worse than Twitters and B) people don’t have that much of an option anyway. In the otherhand, the rebranding failed in the sense that everyone still knows them as Comcast.