A- there was no need to. An island nation on the opposite side of the world didn’t pose an existential threat to all of the major world powers at once. Plus Asians were generally viewed as inferior. Honestly just look at ANY European depiction of them from that time. (Especially the in relation to the ‘White Man’s Burden’)

B- the major world powers have never worked together unless one world gets too powerful. i.e.: France during the Napoleonic Wars, or Germany whenever Germany gets too powerful (WWI, WWII). In fact the British Signed an alliance with the Japanese. This benefitted them both. It eased the strain on Britain’s navy now that the Japanese could be depended on to help protect Britain’s eastern possessions. And the Japanese now had the might of the British Empire backing them up.

C- imperial japan in and of itself wasn’t much of a surprise. China had an emperor. Japan beating a European Power in a war on the other hand. That was a surprise. The never had a modern industrialised European nation been beaten by ‘natives’ in history. The Russo-Japanese war was unprecedented to say the least.