The accepted answer is unfortunately wrong. Why wrong? Emperors are/have been himself/herself the embodiment of Japanese culture so that abandoning the national language would be equal with the blaspheme to and the total relinquishment of Japanese culture, westernizing everywhere, demolishing old shrines and other historical statues and constructions, totally denying the Japanese folk tales and other cultural books, thus it is inconsiderate that Japanese Emperors hit the idea to "westernize" Japan. And according to the OP's source,
Shibata (1985) states that Japanese is so firmly entrenched as the one and only national language that no legal designation of its official status is necessary. Yet at least three public figures in modern Japanese history have suggested that Japan abandon its national language in favor of another (Miller, 1977, 41-45). Meiji political leader and educator Mori Arinori (1847-1889) argued in favor of establishing English as the language of Japan and solicited the advice of one of the world's linguistic authorities (Hall, 1973, 189-195).
some beaurocrats or thinkers not Emperor. The original title of the OP's question was "Why did the Meiji emperor consider switching from Japanese to English?"
"Yet at least three" is ridiculous. So virtually no one even in the Meiji government supported the idea by Mori.
As even the OP's source states, It was one of the very few Meiji government important key figures, such as Arinori Mori(English). (It looks like only Mori alone to me.)
This page illustrates, Mori's clear advocation to pick the English as a national language, (in his letter to the thinker William Dwight Whitney)
The march of modern civilization in Japan has already reached the heart of the nation—the English language following it suppresses the use of both Japanese and Chinese. The commercial power of the English-speaking race which now rules the world drives our people into some knowledge of their commercial ways and habits. The absolute necessity of mastering the English language is thus forced upon us. It is a requisite of the maintenance of our independence in the community of nations. Under the circumstances, our meagre language, which can never be of any use outside of our islands, is doomed to yield to the domination of the English tongue, especially when the power of steam and electricity shall have pervaded the land. Our intelligent race, eager in the pursuit of knowledge, cannot depend upon a weak and uncertain medium of communication in its endeavor to grasp the principal truths from the precious treasury of Western science and art and religion. The laws of state can never be preserved in the language of Japan. All reasons suggest its disuse.
（Education in Japan : a series of letters / addressed by prominent Americans to Arinori Mori. New York ; Appleton, 1873, p.lvi.
Was it successful?
No, as people see today, he failed to convince the emperor and other colleagues.
Why was he failed?
According to this page, a very effective counter was thrown by a thinker called Tatsutani Baba(Sorry, no English wiki available)
Tatsutai Baba's counter proposal was this.(for the correctness of the translation, please ask at JLL SE(hereunder same)),
For many Japanese, it takes enormously time and effort to learn English, since Englishe's construction as a language is very different from Japanese and young Japanese people would need painstaking time and labor power to master English. So therefore, changing the national language from Japanese to English makes their other tasks and learning and job performances less effective.
English training needs time and labor and money so that it is very advantageous for rich people. Ordinary people are busy in daily life so that spreading the English training to all of the people in Japan would be very tough. If we gorge forward such an idea, ultimately, rich and poor would be very divided, ordinary people can not publicly participate, therefore only few portion of people would be able to deal with the nationally important issue and society's.
There would be division between these who use English as the main language and these who use Japanese. Therefore there would be no spiritual harmony in people.
I think there were many Japanese people who opposed to the Mori's idea either like Baba.