Johnny Silverhand is a rock star.
Although he didn't have a record label, a big company agent, or enough money to live in a mansion, compared to bands and musicians with mature business models, he was just an immature pauper—and naturally not a superstar—
But if stardom was the first tier, he was definitely in the second tier, and in Night City, he was an unprecedented rock megastar surpassing the first tier.
Music has the power to move people, and his performances were of the kind that had absolutely no competition. It was precisely because of this talent that he could pull off the feat of attacking Arasaka Tower:
The attack on Arasaka Tower was a very sudden plan. To obscure the truth and evade the ubiquitous Arasaka intelligence network, the plan only truly began when they started the actual action.
The most crucial part of the action, and the very beginning, was Johnny Silverhand's announcement to hold a free concert in front of Arasaka Tower!