You can see exactly what happened in these two photos. The crack goes precisely across the diameter of the suction cup's imprint and nowhere else.

The damage is localized to the site, indicating that the pressure differential on the two sides of the glass exceeded the strength of the glass.

The suction cup pulled too hard on your window and broke it.

And, to whoever considered mounting one of these on your aluminum roof, it will do the same thing there, but the damage bill would be far higher.