SAN FRANCISCO — “What’s going on here @tim_cook?” Elon Musk tweeted on Monday to Tim Cook, the chief executive of Apple, igniting a spat between the world’s richest man and the world’s most valuable public company.In a series of tweets over 15 minutes, Mr. Musk, the new owner of Twitter, accused Apple of threatening to withhold Twitter from its App Store, a move that would limit some new users from downloading the app. The action would amount to censorship, Mr. Musk said, with no explanation from Apple for why Twitter would be blocked. He added that Apple had also reduced its advertising spending on Twitter.With his tweets, Mr. Musk set the stage for a power struggle with Mr. Cook, who holds immense influence over other tech companies through Apple’s dominance. Mr. Musk has a vested interest …
