Yes, his postseason stats are very padded because he was a Yankee and his era as a Yankee they had such great teams, but you can't argue his stats nor his durability nor his worthiness to be in the Hall. 3400+ hits, .310 lifetime batting average. 14 ASG, 5 Gold gloves. 11th All Time in Runs Scored with 1900+. There really isn't any argument here.
DH is a position that is still seen as an outlier position, because all they do is hit - Kind of like a relief pitcher etc.
Now, I will say I am a little surprised he was such a high % on the voting, but not surprised at all he got in so quick.