I don't see how the track was perfect for him and yet nobody else could apparently ride it. If he was handed any advantage at all it was probably through his engine, rather than the track. Muller was a worthy champion though. And, yes, I was there.
I was also at the 1976 final and Muller was pretty sensational in that one, too, coming close to getting 11 points. Hardly the form of someone who had done little to enhance his speedway reputation. Also, if you watch the Ivan Mauger documentary, Ivan's wife talks about how Ivan used to get very stressed about trying to do things that Muller was doing - so he can't have been that bad.
He was also, perhaps, fortunate that his home country World Final fitted nicely after Penhall retiring and Nielsen/Gundersen still not quite ready for World domination. But, in that final, he was so dominant that you cannot dispute his legitimacy. Also, before the final, the general consensus on our bus was that Muller was favourite to win, and, when my friend got him in the sweepstake, everyone groaned and tried to swap with him.
The venue itself was an odd one, though. Not so much the stadium itself, but its location. I went on a Speedway tour and, initially, we were put into people's houses, with the bus parked in a cul-de-sac. Some people (mainly Belle Vue fans as I remember) refused to leave the bus and insisted we were put in a hotel. Eventually we were moved to a town somewhere - I don't even know what town it was! - and put in a hotel, which, I recall, was a long way from the track.