I'll give you a couple of reasons that I've heard over the years as to why Pa is so good.
1. Back in the day (40s-50s in particular) the top 4 wrestling colleges in the state sent their coaches out to local high schools to give clinics as the sport was in its HS infancy. Those areas where the colleges were became the states hot spots. One might surprise you. In no particular order-
A. Western Pa (WPIAL)- Pitt (Rex Peery)
B. North Central Pa- Penn State (Doc Speidel)
C Eastern Pa- Lehigh (Sheridan/Leeman)
D. South Central Pa- F&M (Believe it or not- they were among the top teams in the country back in the day) (Uncle Charley Mayser)
2. The State College system. Used to be known as the State Teachers Colleges. Several of them have dropped over the years. The PSAC was never a qualifying conference but the league tournament was one of the best in the country.
So what would happen is that a kid would wrestle in HS, go to one of these colleges to wrestle and to become a teacher. Would get a job as a teacher and a coach and the cycle would continue in an upward motion.