Disappointment is the result of unmet expectations. Mark has consistently failed to meet achievements in accord with timelines he establishes. Hence disappointment.
It occurs to me that Mark is quite good at misleading. He does have some notable leadership skills but he excels at misleading.
Personally, I have high standards when it comes to truthfulness, transparency, trustworthiness, and accountability. At this point, I am tired of excuses and unmet goals. I have never stopped believing in the project. In my view, Mark has not lived up to expectations.