Is it a possibilty that some proof which was available to the Imams and based on which they gave the fatwa was then not available to the later mujtahideen of the madhab due to which the later mujtahideen gave a fatwa contrary to that of the Imams ?
Sorry for so many questions
Certain Mujtahidin in the madhab would give fatwa on the view of the Imam based on the evidence they had available assuming that the Imam had strong proof for his view, while others would feel that it is possible that these proofs available now hadn't reached him, thus they would give fatwa on another view, very often the view of one of his students.
However, this isn't very common, as the mujtahidin in the madhab had to be very highly qualified.
Sahabah رضي الله عنهم would cling fast to the Sunnah, on account of it being Sunnah, while we discard the Sunnah, on account of it being (just) Sunnah!
Imam Ibn Taymiyya (rahmatullahi alayhi) in Raf’ al-Malam wrote:
“If we were believe that the all the Ahadith of Rasulullah (Sallalahu Alaihi Wasallam) were confined to books, then no Alim knows all that is written in books and nor is it possible for anyone to know all. Instead, at times a person has many books with him but does not know all which it contains. In fact, those who came before the compilation of these books were much more knowledgeable than those that came afterwards. This is due to many Ahadith were authentic in there time but reached to us through an unknown narrator, or with a broken chain, or did not reach us at all…Their books were their hearts which contained many folds more than what is contained in these [present] books. And this is something that a person with some understanding of the matter has not the slightest doubt. (Ahtar al-Hadith al-Shareef p. 173& 186Dar al-Basha’ir al-Islamiya)
"The servant who is unaware of his contemptibility and regards himself as honourable, is truly contemptible"
(Ikmalush Shiyam - commentary of the Hikam of Ibn Ata'illah al-Iskandari)
If Allah had not concealed my faults, and my true self was displayed, people would not even spit on me.