As tough as he looks, Enzo is so nervous that he can't light his own cigarette. Michael does it for him and looks down at his steady hands, realizing that he has the personality and skill set to be a Don.
The novel comments on that, too: "To his surprise, his own hands were steady." Another hint that he was fast approaching his destiny?
I might add that since Mike was a former Marine and for his bravery in battle, Michael was awarded the Navy Cross, he was also featured in Life magazine in 1944. Facing a couple of thugs was a walk in the park for him.
The United States Navy Cross is the second-highest military decoration for valor the nation awards, second only to the Medal of Honor. The Navy Cross is primarily awarded to a member of the United States Navy, U.S. Marine Corps, or U.S. Coast Guard (when operating under the Department of the Navy) for extraordinary heroism in combat.