Inequality exists. Those people fired will be out of places to go. Yes, overall people will become richer, those people are an exception.
That's not a given either. The working masses are many many times more than the business owners in count.
So, while a few business owners can get cheaper with being able to fire part of their employees, those employees will be a bigger number that the business owners who benefited.
As for customers, they'll hardly see any difference (except negative, if they're also part, or their spouse/parents are part, of those workers being fired).
Everybody becoming an entrepreneur is not gonna help either -- there's only so much entrepreneurs a market needs or can support. (It's like everybody becoming an artist with easy access to self-releases on the internet: the end result is not everybody getting into the top of the charts, but, if anything, even those getting there having much fewer listeners that stars did in the past).
Our economies are still growing. Those fruits are just going to the owners of capital rather than the workers.