In the real world they sell the shares at a set price, and real people have to buy all of them for the company to get the money. Real people then trade the stock on the market at prices that are set by what people are willing to pay for the stock. If the founders are making money off of it, it would be them under-pricing their shares in the IPO and then selling them once the company is publicly trading at a higher price. It likely wouldn't work in such quantities as 60% of the entire stock, since then you'd be flooding the market and other people wanting to sell their shares would be undercutting you. Something like that could quickly kill a stock - if the price starts to plummet people are going to suspect that there is something wrong with it, even if it's a perfectly good company. In reality you also have people working in the company that won't up and quit when it changes ownership, so it will keep running.
In game the stock is automatically started at the current value of the company - you get 1 share per dollar of value. But then it spikes up as people buy it. There isn't really an IPO, it just gives the company money. And then when you buy and sell shares you're buying and selling to the computer. And in the game when the original owner sells out, the computer just buys it from him no questions asked. And the company is left without anyone controlling it and will completely stop running unless the next best shareholder decides to take time to control it (even though most of the folks buying stock are wanting OTHER people to control the companies - the stock market is supposed to be a way to invest money for a bit of return without work).