Or one could just incorporate as a for-profit in the first place, and pay a $500k salary. There is basically no advantage to paying yourself $500k at a 501c3 vs a for-profit, and certainly not one that outweighs the many disadvantages. Employees need to pay taxes just as they would at any corporation, and the company needs to pay their withholdings. The only payroll tax a 501c3 is exempt from is FUTA (federal unemployment tax).
Seriously, looking for nefarious motivation here is really grasping at straws.
Because one can cash out through a 500k a year salary