When we first started, the project was brand new on BOINC, there was a challenge, and everyone was rushing to get whatever badge level they wanted. In short, we found a ton of primes because we did a ton of crunching.
The primes do get harder to find as the numbers get larger, but mostly it's because the amount of SR5 crunching we're doing right now is much less than what we did during that initial surge.
My lucky number is 75898524288+1
(I am NOT an administrator anymore, so please don't PM me with questions. I can't help.)