Based on the information provided, it seems there are some potential red flags in this interview. The unusually short duration of the interview, the quiet atmosphere, and the tired expression of the interviewer may indicate a lack of engagement or interest. Moreover, the fact that they did not ask about your previous work or reasons for leaving may suggest a lack of thoroughness in assessing your qualifications. Additionally, the response to your question about the biggest challenge of the position raises concerns, as the interviewer downplayed the job difficulty. While it is difficult to determine the exact intentions of the interviewer, these signs suggest that they may not be genuinely interested in hiring you or that they may not be enthusiastic about the position themselves. It is important to carefully consider these warning signs before making any assumptions, as it could impact your decision to proceed with the company.