According to Uproxx.com, "Josh Brolin has already given Mark Ruffalo credit for convincing him to take the role of Thanos in Avengers: Infinity War, but it turns out there is another actor that deserves a slice of credit..." That other actor is Benedict Cumberbatch. Brolin saw him in a film committing to a heightened character and this inspired him to tackle the role of Thanos.