Step 2 (checking if huge numbers are prime) is a hard problem. Additionally, the author wanted to find a prime that encoded the program that was also notable f

Step 2 (checking if huge numbers are prime) is a hard problem. Additionally, the author wanted to find a prime that encoded the program that was also notable for some other reason (to give people a legitimate pretext to host it). He decided to try to make it one of the largest primes ever discovered, and it was, though it no longer is.