No if they investigate every crash they would be busy.
E.g. to explain Hamilton's crash in Monza last lap, he was pushing way too hard on exit of Lesmo 1 curve. He ran a little wide, perhaps left wheel touched the artificial grass (known as grasscrete) and with the bottom plank scraping the exit curb, he did not realise he had ran too wide this time around. Before he knew it, as he had applied hard on the throttle but was on the slippery grasscrete, the car had spun violently (bottoming out on curb could be a factor) and there was no way he could have caught the car.
Oh ok... Thanks... I thought there are not much incidents happening in races.. Like in Monza, only a couple of incidents and the big one is the Hamilton crash...
Anyway, I guess the FIA is ok with the results provided there are no controversies... It is only when Nelson spoke out and cause all these storm thsi time round... Who knows, such thing might be happening often behind the scene... just that the rest of the "kelong" never ever get out of the walls of the team office....