But the truth is that in those years defence spending was a pretty unpopular expenditure.
I don't think underinvestment can be blamed on any one party. It seems to me like it was a confluence of events that made the west seem like a relatively stable and peaceful place buttressed by what seemed to be strong alliances, and then there was Brexit.
I just don't see where they're supposed to pull the money from. Theresa May's magic money tree? I mean, basically anything they do they're going to be lambasted and constituents are going to feel underserved and unheard. For the average person, if you can't get an ambulance, you can't get an ambulance, whether it's due to spending on defence or spending on immigrant housing, you're still going to blame the incumbent government, and a disingenuous right wing media ecosystem is going to milk it for all it's worth.
I've always thought that coming into government after the shitshow of Brexit and the last lot was going to be political suicide for whatever party it was, and I suspect I'm right.