An alternative reading is that after 13 years dedicated to a single project, the original author is simply burnt out on it, but a new maintainer can start with fresh passion that will last a number of years.

Just because someone gets tired of working on something eventually doesn't mean everyone else will immediately feel the same way.

Did you read the notice on the git hub site? I think he clearly states that he wanted to continue to work on the project, but could not justify it after sources of funding failed to materialize.