Looked this up after seeing it mentioned in The Sizzle, a newsletter I highly recommend signing up for.
Tufte’s point is that PowerPoint mimics the hierarchical structure of big business organisations, which is a bad way to communicate. Information is sliced into logical bits and truncated to the point of unclarity; as the information is passed up through an org structure, slides are deleted until only a brief summary remains. Context is lost; key points disappear; the narrative is destroyed. Or in this case, the astronauts aboard the Space Shuttle Columbia died.
What does Tufte recommend? Give people in meetings a short written report, that they digest as the meeting begins. Then talk, talk, about the real issues.