I didn’t say Manafort was guilty, or that he should have been prosecuted; just that he was the Achilles Heal of the Trump campaign—politically.
His principal clients before Trump were deposed politicians: the Russian-backed President of Ukraine and before that, Ferdinand Marcos.
His primary financial backer was Putin associated Russian oligarch, Oleg Deripaska.
Of course I recall that, at the time Manafort came on board, most to the “Reputable” Republican operatives were shunning candidate Trump. (Yeah, we remember, you cowardly sleazebags.)