My guess is it happened because the generator did not supply clean enough power.
You should use a computer back up power supply, (UPS), between the generator, and electronic appliances until you know your generator set up is safe for your equipment. The UPS is designed to filter the power, and make it safe.
Generally inexpensive generators are not good for supplying clean power.
The ground rods are to protect the user, in the even to a short in the generator. If it functions as it should, you won't need it. If the generator ever fails, and shorts out, it could be very dangerous. Without a good ground, you could become the ground, and that's not going to be good.