Not dumb, this stuff isn't really taught unless you explicitly pursue it.

One note: the return on some companies may be higher and others lower, the issue is that the risk for money in companies is higher.

Very simplistic example: the US government can offer you a flat 5%, a company investment offers 10% half the time, 0% the other half.

One is a sure thing, one is a gamble. The more the 'gamble' the more risk and that is a driving factor in investments. People are willing to take huge risks if the payoff is very large (Look at Michael Burry and the big short)

You can roughly calculate yield from a stock investment. If a stock has a P/E ratio of 20 (i.e. the value of all stocks issued is 20x its annual earnings), divide 72/20 to get a yield of 3.6%. If US government bonds offer 1% yield this stock looks like a deal, but when safer government bonds yield 4% this stock now looks unattractive.

Of course this is a gross oversimplification: earnings can grow, stocks can pay dividends, companies can go bankrupt, and companies have to pay their own bondholders as well as stockholders. But hopefully it shows that a tradeoff between stocks and bonds does exist.

Bonds are much less risky too. So when interest rates were low, it made sense for investors to put money into companies because with bonds you got a tiny return guaranteed vs a high risk but potentially large payoff.

Now, bonds are guaranteeing a 5%+ return, so a non-profitable business is much less attractive as a proposition.