Stryker Software Test Analyst Automation Tester interview questions

Was rejected after 7 rounds of interview. They called 2 times for face to face and other rounds were telephonic or skype. I don't believe they took 7 rounds and then gave a reason about my job instability. If that was the reason, why was I not rejected in very 1st round or would never had been shortlisted. Complete waste of time of employee and employer.