Why militarism is such a surefire winner for populists is an interesting question, to which the answer is probably an unpleasant reflection on human nature. Atavism and racism are the easiest way to political success, despite the demonstrably catastrophic consequences.
For an economically dominant power to allocate its resources under the influence of militarism, and then project the resulting capability for extreme violence on less wealthy or organised states, is the time-honoured way for populist politicins to satisfy the atavistic urge they have whipped up, while minimising the catastrophic consequences at home. UK military power is not for “defence” and has never been for “defence” since the formation of the UK. It is for the projection of military power abroad. The destruction of Iraq, Afghanistan, Libya, Syria and Yemen are all, in varying degrees, the result of the application of UK military force on weaker states.