I watched again the last episodes and something started to head up in my mind.
I saw Lex Luthor enjoying the fight between Black Beetle and the Alpha Squad, then he knew about Blue Beetle being an agent of the reach and Savage bought Mongul down on earth.
So..my idea is that, somehow, Starro Tech was planted in those two and the light controls them, and play the reach just as they played the league..
Blue helped them a lot with the runaways, and just for the record, the scarab didin't trully seemed in control here..
The Scarab didin't betray Jamie back on the reach ship and never obey to anything black had to say to them.
So ..my guess is that Green couldn't do what the scarab never really wanted in the first place and that the reach isn't control the meat, the meat is playing the reach.
I know is a long shot but ..it may be truth?