Why theano UFOs

It does seem that the Fermi Paradox has only two possibilities:

1) We don't see aliens because they are hiding.
2) We don't see aliens because there aren't any.

Number 2 of course divides into three more:

2a) There aren't any because they never evolved in the first place.

2b) They evolved, but destroyed themselves before they could meet us.

2c) They're are out there all right, and they haven't destroyed
themselves, but they never advanced technologically to the point of
space travel/radio astronomy. There's no reason any society HAS TO
get past the paleolithic, much less the industrial.

There could be others, I suppose, but they are probably combinations
and slight variations on the above.