I don't doubt that many proposals were made well before 9/11, but that attack certainly proved a catalyst in getting them approved.

Basically: we want to control citizens > citizens don't want to be controlled > create a scenario in which they want to be controlled > control citizens

Might take a few years between implementation and the desired result, but politics is always a slow march towards authoritarianism.

Also, the fact it was labelled as the counter terrorism act. Not much call for a counter terrorism act of there isn't much terrorism happening. No better way to say "we need this" than an actual terrorist attack happening.