Ahem - it is clearly an "IT fault" if you don't have adequate resilience designed & built into your infrastucture, and power & air conditioning are the basic "life blood" of a data centre. Even if you outscource it all to someone else.
Of course, to do that "properly" isn't cheap - redundant power / UPS / generators, & redundant network links to the "outside the data centre world" . But when you experience issues like today, it is no longer a cost, but an "investment" in your business.
As I have said many times to my customers;
Computer systems have three key attributes - good, fast & cheap - pick any two of the three - as a good, fast system will cost what it costs, and won't be as cheap as compromising what you are trying to do.