The question was NEVER if Hunter Biden violated any laws.
But in order to get there, no one needed to start out suggesting Hunter Biden erred. All that was legally pertinent was the question of the propriety of Biden senior pressuring Ukraine to fire the prosecutor. THAT legitimate question, if it was properly investigated COULD, POSSIBLY lead investigators, in time, to evidence of shenanigans by Biden junior. But getting there did not require starting with that suggestion, and Trump did not make that suggestion - only what was the deal with Biden senior getting someone fired.