

which ones? germany has government spending at 48% of gdp https://en.wikipedia.org/wiki/List_of_countries_by_government_spending_as_percentage_of_GDP so 5% of gdp for defense will be closer to 1/10 of all government spending
going by 2024 numbers, russians putting third of government spending to defence would be closer to 13% gdp
well, i see a large category of infrastructure problems (that will be 99% civilian use anyway - and not only transport, also telecomms, you can even put healthcare training in there) that is solvable by pouring money at them, and now it’s politically convenient to let it rip even among pro-austerity neoliberals. if you want an example of what can this do, look at eastern eu countries and how they changed after funding went in