Illinois runs it's own OSHA program. So, even though the press release says "fed osha" because it's a state plan location for the public sector, the decisions about where to conduct OSHA inspections, and how much to fine locations is initially determined by the state OSHA organization. So, one can safely assume that the inspection could have been motivated by the gun ranges political views.
Having said that, a lot of OSHA regulations significantly impact shooting ranges. The Lead standard being one, Hearing Conservation another, and god knows how many more. Complying with regulations could close a lot of marginal indoor ranges, and increase operating expenses of remaining ranges.