Why must there be an "it" through which TEM waves proagate? Why cannot
they propagate through nothingness?

Because the only thing that can propagate through
nothingness is nothing. That should be clear to
the most casual observer.

Well, yeah, makes sense to me ... but then, apparently not others ...
not 100% sure, but yeah, that is where I am at, at the present time.

First that "sea" must fill the void to give us a "media" (ocean) to sail
... and most certainly a must for RF/light to propagate through!

Regards,
JS

But if nothingness is something (because it has a name) then you can
propagate through it because even nothingness is something so that can be
our "media". In fact it must be the perfect medium because it has a
velocity factor of 1.