The FIA promised this inquiry three days after Abu Dhabi. But work on it did not start until last week. And Ben Sulayem's meeting with Wolff happened a little over a month after the Abu Dhabi race. This is a delay that some in the sport find inexplicable, even allowing for Christmas.
The impression is that the FIA was initially working under the belief that the issue would go away as time passed. Hamilton's indirect intervention this week has dismissed that idea for good.