The key dynamic in State spending is this: the allocation of public capital is intrinsically a political process, not a market or communal process. Thus politically powerful cartels and guilds will secure State funding for their vested interests, and potentially higher-value investments will go begging.
Political allocation of the national income knows no bounds. Politically, there are never any limits. If tax revenues aren't keeping pace, then the State must borrow increasing sums of money to fund its spending. Politicians and their State fiefdoms/private-sector masters, the cartels of finance, defense, healthcare, education, construction, etc. are screaming for more funding; where it comes from is secondary to easing the political pain.
Each constituency, cartel and fiefdom is convinced that they are acting in their own best interests in demanding more State funding and subsidies. As a result, they are blind to the consequence of everyone becoming dependent on the Expansionist State: the collapse of a system that is now yielding a highly negative return on State spending.