The tangential of the field line is the direction of the electric field. From Newton's Law: The acceleration of the charge particle is propotional to the electric force. So the acceleration of the charge is in the direction of the electric field. The acceleration of the particle tell us how the velocity change with time. The tangential of the trajectory is the direction of the velocity ( Not the change of velocity: acceleration). When the velocity of the charge particle is zero, the direction of the velocity is the same as the direction of the acceleration. However, when the velocity of the charge is not zero, the electric field line provide the direction of acceleration (not the direction of the velocity). So the electric field line did not match with the trajectory of the particle.