Big rims, ultra low profile tyres, potholes = cracked rims.
They're low profile, but wouldn't say they're ultra low. 265/45 x 20
I can't remember now what profile I had on my Omega .... 235/45 x 17 if so, the wall is actually taller on the ML that it was on the Omega.
I've had it suggested that straddling speed 'pillows' is the problem
Straddling speed pillows (everyone does it, all the time) might be bad for your alignment, by forcing the wheels outwards from the bottom, but I really can't see how it would crack a rim like that. The tyre would deform, but not enough to bust the rim, surely? If it really was the case, I'm sure we'd see a lot more of this.
Just follow any vehicle and you'll see them doing it, it's a natural compensation to stop one side of the vehicle taking a hit.
The weakest part of an alloy rim is the inner edge of the rim where there is no strength from the spokes. Straddling 'pillows' puts unnecessary strain on the weakest part of the rim. If the profile is such that the tyre absorbs the deforming, no problem, but low profile tyres can result, in the worse case scenario, damage to the rim, which is then usually only noticed when balancing replacement tyres.
I'd rather drive between two of them with one wheel, and drive over the top of the adjacent 'pillow' with the other wheel, which is a pain.
I hate speed humps, 'pillows', chicanes and all forms of traffic calming measures with a passion, as in reality, they are vary rarely well thought out in their planning.