So this article is quite interesting regarding the FIA deal and the Ferrari engine:
https://www.funoanalisitecnica.com/2020 ... refresh_ce
The best summary I could find (from Reddit):
1) Red Bull and Mercedes suspected faul play by Ferrari regarding the engine, but their clarifications asked from the FIA initially amounted to nothing.
2) A FIA-person, who was embedded at Ferrari found out the trick Ferrari was pulling off (bypassing the fuel flow sensor) and forwarded that information to either Mercedes (or Red Bull) who then asked the FIA for clarification, leading to the TD that nerfed Ferrari, and the FIA-Ferrari settlement.
3) To put that into context; the FIA can't issue technical clarifications of their own volition. A team needs to prompt the FIA, upon which they can issue a TD. This FIA-person therefore handed over this info about the Ferrari engine to Mercedes.. allegedly, which eventually led to the TD.
4) Ferrari felt betrayed by this FIA-person (who in their eyes illegally shared Ferrari IP with others) and feel that Toto's wrath was in retaliation to Ferrari vetoeing him as Chase Carey's successor as the head of Formula 1.
5) It is believed (by those in or close to Ferrari) that other (read: most likely Mercedes) engines still operate in a grey area, while Ferrari is now fielding the only truly legal engine.
If this is the wrong thread let me know and I can move it.