1) As stated before, very few champions won in the best car, and Lewis is arguably one of those few in 2008 with the Ferrari having just a bit more pace that year. So he did it under both conditions. Senna, as amazing as he was, only won his 3 titles in the best car, but he proved himself by being fast in the rain and in qualifying....speaking of which:
2) Rain is the great equalizer when it comes to determining driver ability over car performance and Lewis has proven many times (last Saturday most recently) that he is among the greatest in the rain...beating Max by 1.2 secs in heavy rain in qualifying on a 1 minute track is no small feat.
3) Alternative facts? Button did not beat Hamilton all 3 years...only once in 2011; Hamilton beat him in 2010 and 2012.
hang on very "few" champs win in the best car? eh? It's not all about pure pace/speed (look at Ducati in MGP)...it's the overall package, yes speed is important, but so is grip, drivability and reliability. The vehicle that ticks the most boxes is the "best" vehicle. Often the "fastest car/bike" is not neccesarily the best. Hamilton was a tad lucky in 2008, I feel sorry for Massa, he had a lot of bad luck that year.
I know Lewis is good in the rain, most of the top drivers are. I have never said Lewis is not an exceptional driver. But having the best car helps considerably in the wet, over driving a car in the wet tends to lead to disaster. I personally don't think Lewis ever has to overdrive his Merc.
Lastly, read what I said "outscored". in the 3 years they shared the same car Button scored 672 points to Hamiltons 657 equal footing...not many think Button is the GOAT do they? The difference between the drivers is probably very marginal, the main difference is the vehicle and Mercedes utter dominance is a MAJOR point of Lewis' Success...like I said FIVE 1-2s in 7 years...I've trawled the stats and no team I found has ever had that level of dominance in the past 20 years. It's the car, but you have to be a damn good driver that's a given. But I still think Shcumacher is the GOAT (in F1) for a few reasons, he helped develope the Ferrari with Brawn and Todt, Hamilton's dominance coincided with the Hybrid rule change. Scumacher suffered a major injury (leg break) Hamilton has suffered no injuries, Schumacher and Ferrari had more reliability issues I remember Schumacher getting a result with ONE gear working on his car....the Merc could take a nuke and still win (slight Hyperble there!).
just checked stats back to the late 80's
Mclarens Prost/Senna dominance - two 1-2 WDC in a row
Williams three 1-2, only 2 in a row
Ferrari's Schumacher Dominance only 2 1-2s, not even in a row.
So Mercedes has FIVE 1-2 in the WDC out of the last seven years, once again the CAR is the main reason IMO.
Lewis is damn good, best of the current crop...but GOAT? No way.