Monopolies only exist if they are created by the government. If the market is free, or even relatively free, then monopolies cannot exist. Nature does not allow vacuums. The market does not allow monopolies.
The cell phone (hardware) industry is largely unregulated. It’s a free market.
Look at the graph for 2005-2006. (With thanks to Mark Perry for posting.) Nokia is going to crush everybody. Except, they don’t. Along comes Apple with iPhone. Along comes Samsung with Galaxy. Nokia? Nothing. No innovation. Nokia “monopolized” the market in 2005. Now, they don’t exist.
Second note: Are we better off with iPhone or Nokia clamshell cell phone? How much did Nokia clamshell phone cost in 2005? How much does iPhone cost now? How many jobs have been lost at Nokia? How many jobs have been created by Apple and Samsung. Creative destruction. The app market didn’t exist in 2005. There was no job title: app developer. Now there is. Net job gain or job loss?