More likely, he was kept out because the investigation was too politically toxic for his future political aspirations. Thus they spread the “they feared him because he would conduct a real investigation” rumor as political camouflage.
IMHO, he just outed him a a big snake in the tall grass.
If by “they” you include two of my friends in Manhattan DA office and a Deputy Chief at One PP then I suppose they were misleading me over a few beers. And so it goes.