However, he doesn't stay in the shadows for long. He doesn't even remain all that mysterious. Most villains evade giving details and information to the heroes. This is what Brigid and Cairo did after all: neither is entirely honest with Spade about what they want and why. Gutman, however, goes out of his way to detail the history of the bird and his efforts to get it. Where others hide their cards, Gutman willingly shows his, or at least some of them. Even when Spade tries to negotiate with him, Gutman is confident he'll make his escape fine, likely because he's done it before.
And then there's his girth and his speech. While it can be easy to forget what the other characters look like and they all tend to keep their lips shut more than open, Gutman, literally and figuratively, stands out. He's fat, with references to his multiple chins, and even his name: Gutman. His size is his most distinct physical characteristic. Similarly, his speech is distinct from his fellow characters. Everyone talks differently, but they tend to do so in hushed tones. Gutman has not only highly distinct speech patterns, but the mere quantity of words exceeds that of those around him. This man loves to talk, and it's a different proclivity than Brigid whose long speeches are pleas designed to get others to help her and make others believe they're in charge.
However, his size and his speech have no bearing on the novel's outcome. Gutman isn't caught by the police because he was too fat to run away, no doors he's unable to pass through, nor is he caught because he takes too long with a speech or reveals something he shouldn't. He's too careful for that. On the other hand, Spade taunts Joel and Wilmer to rile them up and catch them off guard, and Brigid carefully uses her beauty to charm Archer and, presumably, Thursby and Captain Jacobi. But the big talk and big body don’t get such narrative privilege: Nothing suggests Gutman must be the heaviest, most garrulous character in the novel.
So why is he? On the one hand, it's his greed. The space must be his, just like the Falcon, but it's deeper than that. It's not just a need for space, but the ability to reach out and extend himself. He reached out to a Russian General, the Orient, Hong Kong, and San Francisco, crossing the world in search of the falcon, and, it's insinuated, he has the criminal connections to do so, and money never seems to be an issue for him. Nor does escaping the official police. When haggling with Spade over what to do, Gutman insists all will be well, while Spade insists otherwise. Gutman figures all will be well probably because all has been well for him up to this point.
Gutman's physical traits and habits neatly line up with his motivations and actions as a character. Comfortably corpulent, greedy, far reaching, and, as he believes, safe. He is able to be the man pulling the strings and shows his cards because he's sure he can act with impunity and evade detection and capture.