There are many potential reasons for Facebook to do so. One is to give Facebook legal grounds to remove any content that may expose them to legal liabilities, as suggested by Jordan Wildon (https://twitter.com/JordanWildon/status/1300706794654904320), another - more worrisome - is to allow them to justify censorship by immediately comply with local government takedown requests as hinted by human rights commenter Ananya Ramani (https://twitter.com/AnanyaRamani/status/1300625193191182338). Then of course there's the Australian bill. Either way, the real reasons won't be evident until the new terms come into effect, and even then they might be just a precaution that won't determine immediate action.