Why is that necessarily bad? Does everyone need ongoing employment? Why can't more people build and own a business (or a robot, or other productive capital) instead?
Concentration of wealth leads to the ability to outcompete any small business, increasing the risk of operating independently. It's like playing blackjack in a casino. Even if you could eke out a small statistical advantage, the house can stay solvent longer than you can through volatility (and that assumes an otherwise level legal/regulatory/lobbying framework).
Even Silicon Valley's startup culture implicitly acknowledges this - bootstrapped companies are a footnote. Only those companies with the financial resources of insanely wealthy investors stand a chance at mainstream success. That means the (decreasing proportion) of insanely wealthy people have a growing amount of say in what companies are allowed to succeed.
Perhaps seizing the means of production is the way to go ;)
In all seriousness though, Even starting a small business requires a decently large buffer that most people simply don't have. Hard to build one if you're surviving on mimimum wage + food stamps. Living paycheck to paycheck is a real thing. Especially if you have family
It's very common, we've seen it with e.g. internet providers here; big international ISP takes over one of the major cable companies here, they invest heavily in marketing and go under the price of competitors - and thanks to billions in investment money they can keep that up for years -, the competitors lose money and customers until eventually the big one takes over. Monopoly, and then they start increasing the price again. 5-10 year plans. Amazon can do the same with businesses. Walmart, Target, etc all took local businesses and the middle class out of business when they landed in towns.