It's not the taxpayers money, it's the government's money and the taxpayer is just allowed to use. Taxes are necessary for expenses, like wages for government employees and tanks and bullets. They don't need taxpayers money for investments. They just create government debt for that.

Ever heard of large scale asset purchase programs (LSAPs)? That's the FED buying up investment products like treasuries and mortgage-backed securities and loans to commercial banks and business. Those loans returned negative interest, so those are crappy investments for your government, but they are great for profit of the commercial banks and business.

Have you heard of Quantitative Easing? It's a tactic used by the Federal Reserve to stimulate the economy in times of crisis, by BUYING corporate bonds. Those are loans to corporations, giving a meager return and without providing ownership of the corporation like stocks do. It's a safe investment, but not a profitable one. (It also favors corporations over smaller businesses)

"The Federal Investments Program represents almost a quarter of the public debt outstanding, providing services to approximately 240 Trust, Deposit, and Special Funds."
"In April 2022, the public debt of the United States was around 30.37 trillion U.S. dollars, around 2.2 trillion more than a year earlier, when it was around 28.2 trillion U.S. dollars."
So the US Government now owns around 7.6 trillion dollars worth in investments.

However, you as a taxpayer are not profiting of those investments, because the interest rates are very low. They are designed to 'stimulate the economy', by stimulating corporations. It's another 'trickle down' idea.
If the investments by the government were actually providing good revenue, YOU, THE TAXPAYER would have LOWER TAXES, because the revenue from the investments would pay for expenses.

Solar power is a MUCH BETTER INVESTMENT than the US Government owns at the moment. They could do what I proposed and actually make money for the taxpayer OR they could do what they always do. They will give free or almost free loans to companies like Cypress Creek Renewables and then they get leases on land to build THEIR solar farms and than they sell the power to electric companies, selling the power to the American consumer. That's a simplified version of a system where a lot of companies make a lot of money for their shareholders. I own some of that stock myself.
(And I've just put in an order to buy 10 stocks First Solar @ $60.01)

In the current system (the 2nd I described), everyone makes money,
except the taxpayer. In my proposed system, the government makes money
from it's investments FOR the taxpayer, SAVING YOU MONEY.