What is the wattage of the bulb you are using?
My thinking is that if the bulb wattage isn't too high (100W bulb or less), you should have been ok driving a 2 ohm load while on the bulb limiter, as the bulb would prevent excess current. Other than on the bulb, the amp is not designed for 2 ohms so you should not do that.
So it's possible that the amp came up with DC on the output when powered up on bulb with 2 ohm load. If so, the problem is always avoided by powering up on the bulb first, then connecting the load while unit is powered up.
Still another possibility is that some driver or other part was still marginal and would have failed regardless of the load impedance or being powered up loaded on the bulb.
We can't really know definitively, just surmise.