it crumbled under the opposition.
Hardly that. The 100 hour requirement is still included in AMC1 FCL.210; FCL.215 and is applied elsewhere in Europe. All that happened is that the UK CAA issued an Alternative Means of Compliance that removed any reference to a minimum number of hours.
The logic for the 100 hour figure was the credit awarded to the holder of a PPL holder commencing a modular ATP theoretical knowledge course compared with an ab-initio entrant to an integrated course.