It is demonstrable that the chains of decay of muons and tauons finally ending in a single electron resp. positron. The intermediate stages of the different decays are caused on the one hand by the higher mass = energy and on the other hand on various internal energy of the decaying particles.
Therefore muons and espacially tauons show superior number decays what means that additional particles arise during decay. This additional particles are caused by pair production. The arising electrons/positrons are demonstrable the elementary building blocks of all particles and atomic nuclei.
Thesis The Reason of a realistic View to Particles and Atomic Nuclei