In 1921 I returned from the United States to give public lectures on Tagalog philology, calligraphy, and linguistics. I introduced the word alibata, which found its way into newsprints and often mentioned by many authors in their writings. I coined this word in 1914 in the New York Public Library, Manuscript Research Division, basing it on the Maguindanao (Moro) arrangement of letters of the alphabet after the Arabic: alif, ba, ta (alibata), “f” having been eliminated for euphony's sake."While that quote is accurate, it doesn't tell the whole story as to why he did it. There wasn't any explanation why he linked the script to Arabic but there were some interesting points that may give you an idea of his motive.He writes about the origin of the word "Alphabet" and his seemingly admiration of of other cultures who have names of their alphabet.
The Japanese call theirs the KANA and HIRAGANA SYLLABARIES invented by a Budhist mon in 700 AD which are based on the simple Chinese symbols. The Hindus call their Sandskrit alphabet DEVANGARI meaning "THE CITY OF GOD." (Pangbansang Titik nang Pilipinas pg 11 - Paul R. Verzosa - 1939)Maybe one of his goals to rename the script was to uplift it. He does acknowledge that the writing was indeed called Baybayin by the natives.
The first Spanish conquistadores and missionaries who came to the Philippines after the death of Magellan in the Island of Mactan found that the Tagalogs used to write their spoken speech in their native system called BAYBAYIN, and equivalent of Alphabet; but he litteral meaning of Baybayin is TO SPELL OUT or SYLLABICATE.(Pangbansang Titik nang Pilipinas pg 11 - Paul R. Verzosa - 1939)It looks like he wasn't content with the generic term equivalent of Alphabet. He wanted something more majestic in order to perhaps give the Filipinos a sense of pride. Putting all that aside, it still doesn't really explain why he chose Arabic as a base of the script. He does document that Baybayin is a direct descendant of Sanskrit.
Asia adopted the various simplified and popularized Sanskrit alphabet and handwriting, of which the Tagalog handwriting is its distant but direct descendant.(Pangbansang Titik nang Pilipinas pg 17 - Paul R. Verzosa - 1939)The book is broken down in 3 parts:Part1: Historical BackgroundPart2: The Structure of the LanguagePart3: How to Read and WriteAt the end, there were advertisements. Check out BPI. Mapua also had one as well.