they didnt have to.C'mon son, we all watch movies. That's why the montage exists. You can't tell me they couldn't have done a minute long montage of showing his business expanding and his grip becoming more ruthless. Especially because it's literally all the characterization we get from the character until the third act.
Vulture Keaton says that they went this long without the Avengers ever knowing what they were doing.
thats it.
so you know they was gettin busy!
i dont need to SEE that shyt!