Honestly like…tfp megatron needed starscream to be a twitchy, paranoid, insecure mess, he needed him to feel worthless and expendable and he needed ppl to think little of him because if starscream really truly wanted to, he would probably be a great leader of the decepticons. When he canonically got the chance, he was competent and practical and he didnt have all that personal petty bullshit with optimus getting in the way. Of course megatron humiliated him and belittled him and did his best to undermine him and isolate him, if he didn’t starscream might have garnered some genuine support among the ‘cons and actual fucking sucessfuly overthrown him