How many people change their own oil?
Out of that small fraction of the car-owning public, how many select synthetic oils?
Outside of BITOG, how many people would even consider PP, Ultra, Synpower or Edge?
M1 came to the market early and has been consistently sold under the same brand through many changes in formulation and through the addition of many new flavors.
XOM also has good marketing and a good website, plus if you need a Euro oil, M1 has you covered.
Good luck finding such an oil on the shelf at Walmart of any other brand.
Nobody else has had the marketing sense to do all of this, plus M1 can be relied upon to be a good oil, although that's actually true of the rest as well.
As a consequence, M1 eats every other synthetic oil for lunch in sales.
If I want to claim to be good, I'm going to try to claim that my oil is better than M1 in at least one quantifiable way, even though it may actually be worse overall.