In my years of looking at subsidies and works projects I have sadly come to believe that no matter how many times it can be shown that taxpayer funded rail lines, even highways, are a bad idea, some can not break from the idea that these things are “public goods” which can’t be done in the private sector. The reason they think this is because for the most part this is what they’ve been taught their whole lives. It is a sort of reinforced ignorance.
Then there’s another contingent, the crony contingent, politicians, connected unions, etc. that benefit from “public” projects where there is little oversight of taxpayer money. This group is worse than the first, as the cronies are in it for the cash and power and most likely know the deal.
Many if not most infrastructure projects can be done in the private sector. And since they are done with investor money instead of tax dollars projects are more likely to be done more quickly and with higher quality. The New York subway was originally private. The greatest and most profitable of the transcontinental rail lines was the only one to be done entirely privately, The Great Northern. There are many other examples.