A Saruman won't listen to a Radagast by default.

A powerful Saruman needs to vouch for a Radagast to get other Sarumans to listen.

A bona fide Saruman can vouch for themselves.

It's possible to look like a Saruman if the viewer only looks at you for a few seconds at a time.

A commanding leadership vibe.

Saying things like "if you want to survive when swimming with sharks, you've got to be a shark, that's just the way the world works".

Flexing for the camera.

That allows you to get them to listen to an argument that they'd otherwise reject as too Radagast-y and woo.