The UK like the United States is a maritime power and to be successful in other continents and regions around the world

They need continental allies to provide the manpower and resources to fight continental Wars

It's a lot more expensive for a island nation and maritime nation to engage in Wars on the continent

Than it is for two continental powers

As for the British I would say it was a mistake to neglect the army but maritime powers tend to have strong navy's but weak armies

Same goals for continental powers like France and China who have strong armies but weak navies

I would say only the USA is the exception to the norm