1. Apologized to me after two interviews

Two interviews in total. In the second one, they asked me to suggest areas where the company could improve. In the end, they told me to wait for their notice and that I could start work. Then, on the day they were supposed to notify me, they apologized and said I hadn’t been accepted. At the time, I even specifically asked whether I could start, and if so, I would turn down my other interviews. They said it was confirmed, but in the end this happened? Although I don’t really understand what happened, please don’t say that someone can start and turn down their other work or interviews before it’s confirmed. This made me wait for nothing for a week—isn’t a week still time? During that time, I don’t know how many interview opportunities I turned down. I can only say that I feel terrible and had to leave a comment. Thanks~