Well, in the end, the Brits won. And that’s what matters.
In the early years, money, stupidity and hope were at the heart of it.
Penny pinching between the wars (look at the way the RN paid off its officers and men) by Britain. Ably assisted by the Depression.
Stupidity, that ensured that those who presided over the penny pinching while aware of the treaty breaches by Germany didn’t bother to consider the effects of Germany building its armed forces while Britain was running its armed forces down.
Hope, that somehow the inevitable consequences of money and stupidity wouldn’t end as they were bound to. Chamberlain exemplified hope with his grand ‘Peace in our time’ statement.
LRDG, commandos etc were only factors long after the war began.
In the early years, after Dunkirk, what mattered primarily was the sea war. A year or two later the air war began to be important over Europe, after the fairly brief but critical Battle of Britain.
Germany, and for that matter Japan and the USSR, never had to confront the immense strategical and logistical issues Britain had across most of the planet.
Stalin had limited naval issues, and no strategic bombing capacity or campaign.
Hitler had nothing to worry about in the Indian and Pacific Oceans, apart from some fairly pointless actions by commerce raiders. He never ran a strategic bombing campaign that really mattered.
While Hitler was pulling Mussolini’s nuts out of the fire in Greece in mid 1941 preparatory to Barbarossa, he didn’t have the same problem that Churchill did in committing troops to Greece for essentially pointless political reasons (taking them from North Africa where the Germans had gone largely to rescue the eternally ambitious but incompetent Italians from another disaster).
Churchill knew when he committed troops to Greece that Japan was likely to attack. So did Hitler. The difference is, it wasn’t a problem for Hitler, and he didn’t have to dispose his forces against potential threats in Asia.
Apart from the U boat war, Germany pretty much played out its war on land, most of it out of reach of Britain in the early years.
I’m not Churchill’s biggest fan by any means, but if you take him as representative of Britain then, given what he had to deal with, he did a bloody good job. Not one without typically Churchillian errors of arrogance and stupidity, but overall probably a bloody sight better than Chamberlain or Halifax could have managed even on belly full of grog.
The question might be, why did Germany do so badly against British forces which had rather more to deal with than Germany?
And that goes to Germany biting off a lot more than it could chew in Europe.
