If this post is to be believed, Deobandi schools initially offered courses on the hard sciences but it eventually was phased out. Why did this happen?
Hi, I'm the OP from the post you've linked.
The Deobandi schools never included hard sciences in their curriculum, they modeled their syllabus after the Farangi Mahalli syllabus with the exclusion of hard sciences.
The Farangi Mahall ( translated: Foreign Quarters) was used by Europeans mostly French businessmen to stay during their visits to Lucknow or Delhi. Eventually the land and the estate was gifted by the Mughal Emperor Aurangzeb as jagir to Mullah Qutubud Din who was quite influential in the Mughal court and also helped Aurangzeb in his compilation of his fatwas the Fatawa-i-Alamgiri. Farangi Mahall thus housed one of the most influential families in the Mullah sphere, and who set out to carry their own activities in Lucknow far from Delhi.
Farangi Mahall is an important predecessor to the Deobandi schools, because they have set the template which was copied by Deobandi and other Islamic schools.
Combination of Religious and Mystic learning. ( ie. Islamic law and Sufi practices)
Organiized syllabus comprising of two categories manqulat ie transcribed or copied subjects, and ma'qulat rational sciences. This helped bring structure to Islamic schools, because traditionally the definition of an alim ie. a learned man is indistinct. Anyone can be an alim if they are knowledgeable enough. The syllabus of the Farangi Mahall determines how they acquired this knowledge.
The issue of certificates for completion of programmes.
Independency of the Farangi Mahalli family- even though they accepted donations from princes they were not serving under any one family or king, this allowed them to be independent and pursue their own goals instead of sucking up to local rulers.
Lastly and most importantly the shift from Delhi to interior Uttar Pradesh. Delhi was no longer seen as a centre for Islamic knowledge and growth and the Ulama moved into the villages and smaller towns for employment.
The Deobandi schools otoh though heavily inspired by the Farangi Mahalli system derive their motivation from Shah Waliyu'llah who is considered the father of almost all the Islamic revivalist schools of South Asia. Shah Waliyu'llah was a contemporary of Muhammad ibn Adal Wahhab, founder of the violent Wahhabi/Salafi sect of Saudi Arabia, and during his visit to Arabia for Hajj, Shah Waliullah was influenced by Wahhabi ideology. He believed that there was a lack of study into the hadis and the hadis are the absolute standard for Islamic life and the degradation of the Islamic empires around him further strengthened his belief that the collapse of Islamic rule everywhere was because people had strayed away from the Quran and the Hadis.
Waliy'ullah's stand thus became the default stand of the Ulama who came after him. The Deobandi school is a direct offspring of this thought, just like Waliy'ullah they do not believe that hard sciences or rational sciences are the need for the hour, they believe that the Quran and Hadis must be studied in depth for one to be a good muslim.
Source: Islamic Revival in British India Deoband, 1860-1900 - Barbara Daly Metcalf
Deoband did teach subjects like Mathematics, Astronomy, Tibb (Medicine) which were part of Dars-e-Nizami syllabus, but it didn't opt for hard sciences. The reason wasn't because the founders were opposed to the idea. Far from it, but it was a decision reached after much deliberation. It was to plug the gap in the market for education at that time. British Government were opening up institutions to teach standard secular and scientific subjects to prepare people for adminstrative jobs, so they decided to focus on traditional religious education as this wasn't being taught elsewhere and they considered it necessary for the preservation of muslim social, religious and cultural life. It was from this period onwards a divide begins to appear and continues to this day in how education was viewed by people - segmented into non-overlapping religious and secular domains. Before this period, an educated person whether muslim or otherwise had a rounded education. The establishment of MAO College (Aligarh Muslim University) later on was to bridge this gap to some extent between the secular and religious domains.