It amazes me the wide variety of ways that our civilization can be negatively impacted and our accustomed way of life comes to an end. Power grid failure will, of course, cause a lot of problems. Plus many problems can cause a power grid failure. The book "Nothing to Envy" tells how North Korea had electricity all over the country. When the Soviet Union collapsed, shipments of fuel for North Korea's electric generating plants stopped. Generating of electricity became spotty. Then when the electricity was off, people stole the electric lines and sold the copper. Gradually the nation (except the capital city and a port) went dark. So an electric grid failure could happen suddenly (EMP, cyber attack) or gradually (theft of equipment, lack of maintenance).

Good you are prepping. Even having just food and water will be very helpful in a time of crisis.