If someone has very large capital, of course he knows the impact of the investment itself, where he will choose, of course he will choose the long term rather than the short term. Of course he already understands the risks he is taking and can take responsibility himself. It's a shame that your friend actually quit his job. This job can indeed make quite a lot of money if we have the ability to predict or analyze it. However, it takes time or quite a long process to achieve all of that, we cannot or just in an instant or overnight we can achieve all of that.
I think most of the wealthy people have huge sums of money are more interested in trading instead of investment and those who have a limited amount of money are interested in investment as they think that if they keep their money in beneficial assets then after some years they will be able to make their economy better.
Those who leave their job for investment or trading are the foolish person and they will realise about their mistakes if they continuously lose money through trading and will then be feeling sorrow to leave their job.