The HR staff were nice.

The hiring manager seemed distracted during the interview, perhaps because they were very busy that day?

All the questions were probing for internal information about the company currently providing the service, which made me feel that they were not really interested in learning more about the candidate.

The technical oral questions ranged from easy to difficult. If the answer was not what the manager wanted or was incorrect, there were no further questions, regardless of whether it was only the first question.

Is this really an appropriate way to assess technical skills? Even experienced experts might answer a simple question poorly or forget the answer.

It is like English vocabulary: I think you might not be able to pronounce or spell a word that seems simple to you, but is it difficult or intermediate for you?