So yes, underfunding is simplistic in hindsight, the reasons were much more complex at the time.
I don’t buy that. Head in the sand would be a better explanation as would willful ignorance of the world around you. The war in Georgia in 2008, the war in Ukraine started in 2014, the sub threshold warfare game of sabotage Russia has been playing with Western Europe should have been more than enough to make anyone in Europe who cared to look aware that you partnered with a foe and not a friend. It however was business as usual with the bear as long as the energy spigot was open, much was ignored.