The same thing happened with the Iraq War: Casualties of the Iraq War

For a long time, they tried to get away with about 100-200k, but in 2007 the Opinion Research Business (ORB) poll came out with an estimate of a million dead due to the conflict. IOW, a 5-10x multiplier. That's probably the most reliable number, and there are a couple of reasons why we might believe that.

First, I have never one single time heard any official or "expert" dispute it, then make an argument in favor of another number. They do not want to "Streisand" the issue then lose on the merits.

Second, you can see right on that Wiki page where They're trying to hide it. Look at that nice, neat table labeled "Scientific surveys". It does not include the ODB poll, even though the fundamental concept of extrapolation via survey is precisely the same as the three listed. Leaving it out is a crude but effective trick.