Ford didn't meet the homologation rules. They simply "promised" to produce and sell 36 (or w/e th number was) at some undisclosed point in the future. At the time when they entered le mans they hadn't produced a single one for the market if i remember correctly.
It's absurd to make racing so boring and expensive with all those sefety regulations, but at the same time not remove a tree that's directly behind a armco barrier, when this is way more dangerous than crashing at 50kph higher speed. Removing a tree is also not very expensive.