Huh? How on earth does Eritrea gain independence at the height of Italy's colonial empire?
Instead of fascism, the socialist party rise against monarchy and install a republic. The entente powers, still weary after WW1, decide to not get involved.
The new italian goverment, led by Gramsci, decide that colonies are inacceptable and contrary to socialist doctrine. So they set out to make the italian possessions indipendent, after a period of preparation.
In the '30s Erithrea is awarded indipendence (under a socialist goverment, of course...).