(i) In Belgian Law, Force Majeure must be not only unsurmountable but also impredictable. Rain was even less unpredictable that it had been raining since 2 days (causing some landslides in the circuit facilities and parkings, but this is another story…) and that all weather forecasts made it very clear that it wouldn’t stop before Sunday evening or Monday morning. There is clearly no Force Majeure to the case in point.
(ii) FIA rules look like an open bar to internal machinations, just like “no cancellation after 2 laps”… so let’s go back to language definitions: GP implies a race, yet what is a “race” ? It is “a competition between runners, horses, vehicles, etc. to see which is the fastest in covering a set course”. Nothing like this took place on Sunday. In addition, FIA rules can not break Belgian public order. Also, they remain unclear: unclear law, “obscuri libelli”: prohibited.
(iii) This story of 2 laps actually leaves the decision to only one contracting party, which means that there is no actual contract. In law you can’t say “I commit to do this only if I want”, this is probably an abuse, but for sure one-sided (“léonin”). Prohibited.