Flash is Facebook's (yet another) attempt in competing with Snapchat
It appears that Facebook has finally come to terms that it can't replicate or outperform Snapchat's success in the US and established markets, since the company has changed its strategy in this mini-war quite significantly. Instead of trying to take on Snap Inc. in first-world countries, Facebook created a new app, named Flash, marketed towards developing markets. The app is first launched in Brazil and will later make its way to other developing markets. Facebook has yet to disclose which ones exactly.
The main benefit of Flash is its size. Its creators claim that it's “less than 25MB”, which should prove lightweight enough for countries with slow data networks. This could have been the main reason for Facebook to create a Lite version for both its core app and its Messenger.
It appears that Facebook is trying to gain a foothold in areas where Snapchat has yet to become as solid. This should allow it to grow a steady user-base before Snap Inc. even tries to. It is still unclear if this effort will succeed, or it will be yet another flop in Facebook's attempts to topple the ghost.