Egoism means that your favour yourself in your actions and you love yourself. This is completely natural and there is nothing wrong with that.
The problem is when you build your success only on the failure of others and employ violence to reach your goals. The problem is being a dick and not being an egoist.
People that own a lot of money are often called to be egoists. But in a free economy your success is build on providing valuable services. So if you work a lot and make a lot of money in such a market, you are not egoistic, in fact you are doing everybody a favour. Actually you are an egoist if you choose to not work and use your wealth to relax. Now I am not advocating against slacking around at all. We should all enjoy life and be egoistic enough to do so.
When the rich get egoistic and stop working that also creates opportunities to be filled so other people get a chance to prove they con provide a service of similar quality.
Of course our economy is not such a hypothetical free market economy and there are plenty people that get rich on the cost of others. But the correct term for them is not egoist, it is asshole. And there are plenty of things wrong with being one.