Hiring is an exercise in risk management. Hiring managers want the best hire possible; candidates want the best job possible.
But hiring managers, and employers in general, routinely forget the candidate’s perspective.
For a candidate, the decision to take a job is somewhere between buying a car and buying a house in importance. They (understandably) want to kick the tires. You would never sign a contract without reading it, and neither would a good candidate. Would you expect them not to? Would you even want to hire someone who wouldn’t do due diligence on a massively important decision? Taking a job is a legal agreement with huge ramifications.
But too many hiring managers take it personally when candidates have real questions and want to know real things about the company. They start to shut down if the client hits too close to home. They feel like the questioning candidate is overly intrusive.