NOV interview questions

I interviewed for the job and had a great first interview. After that I had a in person interview at their corporate office. Following day I was offered the job and wasexplained pay and benefits by the hiring manager. I was told that I will get a written offer letter the following day. After waiting for more than 2 weeks I got an email from HR saying “ We regret to inform you, that due to unforeseen business demands we are rescinding verbal offer extended for Project Manager with NOV.” I found this extremely unprofessional from a major company like NOV. I really looked forward to the job because I worked extremely hard for the interview and my family was extremely excited for the job. I had almost given my 2 weeks notice too because I had such a great interview with the hiring manager and the hiring manager was in constant communication with me telling me that I will get the offer letter soon. I would recommend NOV HR to be more professional and not offer jobs to people unless they will be hired. This is a very unethical practice and really affects the candidate mentally and emotionally.