[DC 86]

I have no idea what her plans and motivations are, but there's no reason to assume she will be a "one and done". In basketball players are essentially obligated to play one year in college before being drafted by the NBA, likewise three years in football. In baseball most (although not all) players who choose to go to college do so in hopes of improving their draft bonus relative to what they are offered out of high school.
In Ledecky's case there were no barriers to turning pro right after the Olympics and her earnings potential was already extremely high (easily seven figures) yet she chose to enroll at Stanford, so obviously she sees value in being a student athlete, and that value only increases the longer that she stays at school.

[DC 86]

I have no idea what her plans and motivations are, but there's no reason to assume she will be a "one and done". In basketball players are essentially obligated to play one year in college before being drafted by the NBA, likewise three years in football. In baseball most (although not all) players who choose to go to college do so in hopes of improving their draft bonus relative to what they are offered out of high school.
In Ledecky's case there were no barriers to turning pro right after the Olympics and her earnings potential was already extremely high (easily seven figures) yet she chose to enroll at Stanford, so obviously she sees value in being a student athlete, and that value only increases the longer that she stays at school.