One weak interview is not automatically fatal because decisions are usually based on the full set of evidence. The important distinction is between a case that felt uncomfortable and a case that showed repeated failure on core skills.
Needing one or two prompts, making a calculation mistake and recovering, or giving a rushed recommendation can still coexist with an overall positive evaluation. A case where you could not structure, interpret data, or respond to coaching is harder to overcome.
Your other interviews matter, especially if they provide strong independent evidence on the same dimensions. Firms also discuss patterns: was the weak performance isolated, or did multiple interviewers see the same concern?
At this point, there is little value in reverse-engineering the vote. Write down what you would improve if you need another interview, then wait for the actual decision.