Longo is only the S&C coach for football. ND has other S&C coaches for the other sports. They also have athletic trainers, team doctors , kinesthiology professors, physical therapists, etc. In other words there are many many people at ND that are experts in strength, biomechanics, athletic performance, etc. The notion that they all are missing some secret knowledge that is leading to all these injuries is a huge stretch.
It does seem uncanny, admittedly, how many injuries they have. But ND is more than covered when it comes to pros in the field that are available to consult on potential issues. Their training programs and protocols are always under review, based on the best research. As frustrating for fans as it is, just gotta trust they know what they're doing.