SB Nation's Maize N' Brew has an extended history explaining "why Notre Dame sucks so much." It's quite detailed and hilarious ... unless of course you're an Irish fan. In which case, don't read this:
In 1947, both Notre Dame and Michigan fielded undefeated teams that traded spots at the top of the AP poll for the majority of the season. Notre Dame, by virtue of non-conference cowardice, did not play a bowl game that year, while Michigan went out to Pasadena and thumped #8 USC by 49-0.However, as was the custom, the AP title was given out before the bowl games, and the press had already awarded the trophy to Notre Dame. In a poll conducted after the bowl games, the writers decided to reverse that decision and give the title to Michigan citing a better offense and the shellacking of USC. Notre Dame, being the cheating, lying, sacks of suck that they are, still has the AP trophy from that season and sites that year as a National Championship year despite the second, more accurate poll.