  WMAP's detection of the Sunyaev-Zel'dovich effect at a much reduced level
among several large samples of rich clusters is interpreted in terms of
conventional physics. It has been suggested that the central soft X-ray and EUV
excess found in some clusters cannot be of thermal origin, due to problems with
rapid gas cooling and the persistent non-detection of the O VII line, but may
arise from inverse-Compton scattering between intracluster relativistic
electrons and the cosmic microwave background. In fact, recent XMM observations
of the soft X-rays from Coma and Abell 3112 are equally well fitted by a power
law or a thermal virialized gas. Therefore the missing Sunyaev-Zel'dovich flux
could partly be due to an overestimate of the central density of virialized
electrons which scatter the CMB. Synchrotron radiation in an intracluster
magnetic field of strength of a few $\mu$G is responsible for significant
additional electron energy loss. Equipartition between relativistic particle
and magnetic field energy densities is a realistic possibility. GHz radiation
data from a Coma cluster halo yields information on the high energy steepening
of the cluster relativistic electron spectrum. Cluster microwave emission in
the WMAP passbands by higher energy cosmic ray electrons and gamma ray emission
from an accompanying cosmic ray proton flux are also considered. The energetic
electrons could originate from AGN jet injection, then distributed cluster-wide
by Alfven wave sweeping, with accompanying {\it in situ} Fermi acceleration.
