How you know a person's performance is good a not by just looking at their resume?

Talk is cheap. You only know a person's performance during the real job itself after a certain period of time of trials.

Retrenchments is also rampant nowadays not because people are not performing when the market is saturated and depressed.

Frequent change of job is very normal these days with bosses adopting Elon's way of hire and fire madman approach.

Also there are companies who hire and provide minimal training but expect applicant to run like a pro on first week of hiring.