It’s funny. Of all the jobs I’ve been ambitious for, this is one that never crossed my mind.

Meaning of the quote

This quote means that the person (Edmund S. Muskie) never expected or dreamed of doing the job they now have. Even though they have been ambitious and wanted other jobs in the past, this current job is one they never imagined they would end up with. It's surprising and unexpected, but they find it funny that this is the job they have now.