As someone with a degree in Forestry and coupled with many a wildlife management classes, there are several factors that contribute to turkey nesting success. Some, not all, are; weather, nesting cover and predators.
Nesting predators account for a vast majority of nesting failures. Racoons, opossum and skunks are the main predators that destroy nest by eating the eggs laid. Coyotes are the number one predator that kills the hen as she sets.
Trapping and removing these predators greatly increases the probability of nesting success. However other factors such as weather and cover is of major importance also. But a very well known fact is, if the eggs are eaten and/or the nesting hen is killed, there will be NO Polts.
A ton of research (by educated professionals) has been conducted by those such as Dr. Grant Woods, Dr. Chamberlain and others. It would do a lot of good for turkey hunters to read up and learn the complexity of management practices.