Reaction coordinate diagram of an EAS reaction

Below is a reaction coordinate diagram showing the reaction of benzene with an electrophile.  The intermediate formed is sometimes referred to as a Wheland intermediate.  Remember that this intermediate is not aromatic, even though it is somewhat stabilized by resonance, so it is much less stable than the aromatic starting material and product. Anything which stabilizes the Wheland intermediate also lowers the energy of the transition state.  This reduces the activation energy, thereby speeding up the reaction.