However for the case of people earning salaries, do you think there is a way they can be really rich without owning a business and or is it compulsory for one to be own his own business
It is still very possible for a salary earner to invest some from the salary they earn. It will require a lot more sacrifice because unlike being a business owner that can have access to money and no fixed earning, a salary owner having a fixed salary will need to cut some other expenses to have enough for investment unless the job is very well paying which is not much as well.
A salary earner will also need to be very strategic and careful with what they invest in, so not to waste their salary years on something that has no or very little ROI.