Notice that the electron is 180° out of phase with the incoming light wave. That is because it has a negative charge. If it were positive, it would be exactly in phase (assuming we ignore damping terms, as done in the Feynman Lectures).

As stated in the interactive, the amount of light that a single electron in an air molecule (N₂ or O₂ for example) scatters is very, very tiny. For that reason, the forward-propagating wave has basically the same intensity as the incoming one.