That quote is quite ironic to tell the truth. Peñalosa created a public transport system that's overcrowded and unsafe. Nobody wants to use it, but many have no other choice but to use it.
It's not a failure in terms of the number of people that use it, but when the seats are full and the standing passengers are jam-packed like sardines, it's definitely nothing to brag about, and you certainly won't find the rich using it.
Peñalosa also introduced Pico y Placa (https://en.wikipedia.org/wiki/Pico_y_placa), a system that does not negatively impact those who can afford to own two cars, and forces the remainder of car owners to use the atrocious public transport system every other day.