Fullstack Labs Senior SysAdmin interview questions

I went through all the processes, passed all interviews, the challenge and put in a lot of time and effort, the made me an offer which I accepted, have me waiting 2 months to start interviewing with clients, at the end they withdraw the offer and got away with a simple mail after all I went through in their process, for me it was a very unprofessional way of doing things because I told them I had no issues waiting a little bit more.