The weight of the 2" line on the wye branch probably caused the split. An expansion joint or a simple riser clamp secured to the line at the plate level of the immediate floor above would have prevented the crack. Recently fixed a broken horizontal 4x2 wye where the branch ran to an 1/8 bend which ran horizontally to a washing machine. The washer line wasn't properly hung. The eventual sag on the line accumulated water and split the wye.
Don't see too many cracked fittings, but I have seen a number of cases where the pipe sheered right below a fitting. This was due to the run of bad pipe from the '80's made with non virgin ABS resin (as in ground up old telephones and such). I remember when the claims started coming in with the unhappy coincidence that the manufacturers responsible were all out of business. Doesn't that figure!