It is pointed out right at the beginning of the wikipedia article that the country was already in a state of civil war.

"By October 1862 Emperor Tewodros's position as ruler had become precarious: much of Ethiopia was in revolt against him, except for a small area stretching from Lake Tana east to his fortress at Magdala. "

I don't see how the issues were trumped up? And I don't see any foundation to the claim that the country was left in bloody civil war?

It seems to me that the expedition mainly succeeded because the country was already divided, and the British were able to barter cooperation from the vaious other fractions.