What is the definition of failed? I knew of one millionaire (due to personal patent defenses) who has run a company over 25 years and has yet to make a profit. His employees and customers see it as a success, but for the rest of us, no profit = failure.
The question is, what are the odds a "founder" will fail and what is the impact of multiple attempts on his/her success rate? Can't recall the source, but seems like those that fail are more likely to fail again.
Just think about it. You're not able to identify what's important and how to execute it on a daily basis with startup 'A', but all the sudden, you've learned your lesson. Closed the door on A and applied all this knowledge to B.
Many successful companies started in one product line/industry, made a change and became very successful. Should that transition be considered a new startup? Maybe the odds would improve on the percent of successes if it were.