Presumably the tax payers would have procured something themselves, if you'd have left the money into their own pockets.
See how IBM was on the path to inventing electronic computers for business and accounting, but got pre-empted by the militaries' needs and procurement.
In the counterfactual if there hadn't been a war going on, presumably businesses would have had even more needs for international business machines.
The counterfactual is that the investment required was beyond what even IBM could consider to spend at the time, to the point that even with "guaranteed buyer" in form of military procurement there was strong opposition towards going into "niche computer business".
Military/government procurement provided the demand for which private entities could provide, money and other resources at level that private market never managed.
Without large injection of money supply there's not much extra dollar to chase and safe investments sound like better bets.
The incentive was US Navy feeling embarassed at how "country that invented the airplane" had shitty showing in aviation in 1914, and ultimately deciding to invest heavily in area now called Silicon Valley.
This provided demand for products and services that simply was not there in private form, allowing way riskier investments - all the way to 1980s Silicon Valley was mostly riding downstream of military procurement (Can't source the quote right now, but Sun microsystems be-or-not-be was landing a contract for NSA for Unix workstations - because NSA could frontload an order for few hundred if not thousands workstations)
