While the reasons behind the Technocracy's breakdown are fairly clear -- the removal of the brain (New World Order) and nervous system (the Syndicate) in any body is liable to lead to the collapse of the body -- the infolding of the Traditions is somewhat more obscure and convoluted.
In the early days of the Long Night, Set decided that any Mages not on his side needed to be either converted to the cause or destroyed. Set then hand-picked Tremere, Setite, and Assamite assassins and sent them out with the mission to eliminate the present Mages from the face of the Earth. Many of the assassins died the Final Death, but many of them succeeded in destroying their targets too.
So the number of Mages, particularly Tradition Mages, was markedly reduced within the first ten years of the Long Night. Only through the Resistance did any Mages come into frequent contact with one another, and through this network, new groups formed according to philosophy, rather than style of teaching.
Today, these groupings are mostly recognized by the Mages as the replacements for the Council and Technocracy, and while the number of Mages is back on the rise, these groups are still tiny compared to their predecessors. Styles of teaching linger as the remnants of the former days of the Traditions, but only along the lines of single teachers. The new Mage associations are generally not so much divided along lines of cosmological beliefs, but along philosophy of life and priorities.