Also I can't understand why any of the multiple weather satellites would not have picked up contrails.
Contrails only form under specific atmospheric conditions. Those conditions were not present in the Southern Indian Ocean when MH370 was lost and hence no contrails would be visible.
Contrails are very narrow and probably outside the definition as seen by weather satellites.
Geostationary metsats do not have the resolution.
Contrails are large enough to be seen by both low-orbit and geostationary weather satellites.