Why does the Edwardian era imply king Edward VII?

Short but very distinctive period

King Edward VII reigned relatively shortly (1901-1910) and was not particularly remarkable monarch, yet his era (sometimes extended till 1914) is a very distinctive period, separate from what happened after that and also from previous Victorain era.

Sharp differences with what came after are of course easy to find. Edwardian era was relatively prosperous and peaceful, and after that came horrors of WW1, then turbulent and "lean" years of interwar period, another war (WW2) and after that dissolution of British Empire, with Britain gradually becoming second rate power in the world.

Differences with previous Victorian era are not so pronounced, but they do exists and are significant. Above everything else, we must mention technology. As a opening decade of 20th century, many of the inventions that would define it are introduced in this first decade. Internal combustion engine running on petroleum derivatives (gasoline, diesel, fuel oil ...) gradually started replacing steam engine. Automobile was a design of previous era, but fist appearance of cars and trucks in any significant number came in Edwardian era - they were no longer eccentric novelty but a new and relatively practical thing. With them came flying machines, both airplanes and various types of balloons and zeppelins. Note that Wright brothers had their first flight in 1903, by the 1910 in practically every major world power there were flying pioneers using either imported or self-designed planes. "Lighter than air" machines like zeppelins also became a thing - with the introduction of the engine they could move a great distance on their own power. Another thing that changed 20th century was radio. Although invention of the 19th century, only in 20th century it became practical enough to be used first in military and then commercially. Thanks to the radio telegraph, in Edwardian era news started to travel much faster even across the ocean and from distant parts of the world. Before that, they relied on cable (like Transatlantic telegraph cable). Now, news could came from more remote parts of the world (Australia for example) , and even from the ships. Electrification of street lightning as well as homes also picked up significantly in Edwardian era. This also did start in Victorian era, but again only in Edwardian era it ceased to be a novelty and became real, practical deal.

Politically, era was also very significant. All major factions and conflicts that would lead to WW1 and WW2 were already developing or were developed in that period. Britain was still regard as top sea (and world) power, but that lead was now challenged by unified Germany and US. It should be noted that by the end of New Imperialism almost every possible piece of land on the planet was captured by colonial powers. Those that came latter (especially Germany) didn't get much and of course were unsatisfied, therefore desiring a new distribution which was almost impossible without the war. Trouble was also brewing in the Balkans, with the desire to liquidate Ottoman legacy with 1908 Annexation crisis and latter Balkan Wars of 1912-1913. Finally, we should also mention Japanese victory in 1905 Russo-Japanese war, which showed that arm's superiority of European powers is not something that should be taken for granted. All of these wars in Edwardian era cemented idea (and partially practice) from the late 19th century that future wars would be wars of massive conscripted armies moved by railways and other means of industrial transportation.

Finally, it should be noted that while Edwardian era retained some vestiges of feudal system, with ruling classes in many countries being from nobility (especially in Britain, Germany, Russia and Austria-Hungary), it was becoming clear that this could not go on much longer. Capitalism has already taken hold, and new ideas, like socialism(communism) and some precursors of fascists and national-socialist thought, were already spreading widely. Overall Zeitgeist of the era was that something had and will change very soon, and that current state of affairs is just a brief pause, which became self-fulling prophecy.