Electrons and photons are indeed both excitations of the electromagnetic field, but they possess different properties, including their rest masses.
In the Standard Model of particle physics, electrons are considered elementary particles with a nonzero rest mass. The rest mass of an electron arises due to its interaction with the Higgs field, which is responsible for the mechanism of mass generation in the Standard Model. The Higgs field provides a mechanism by which particles acquire mass, and in the case of electrons, their interaction with the Higgs field gives rise to their rest mass.
On the other hand, photons are particles of light and are considered massless within the framework of the Standard Model. Massless particles, such as photons, travel at the speed of light and do not interact with the Higgs field in the same way as massive particles. Therefore, photons do not have a rest mass in the traditional sense.
It is important to note that while electrons and photons are both excitations of the electromagnetic field, they have different properties and behaviors. Electrons have both particle-like and wave-like characteristics, whereas photons exclusively exhibit wave-like behavior. The distinction in rest mass between electrons and photons arises from their distinct interactions with the Higgs field and the properties attributed to them within the framework of the Standard Model of particle physics.