The A/P tripped due to the AoA disagree, and MCAS started running 5 seconds later.
As to the other comments, many people fail to recall that there were two accidents. While the Lion Air crew may be given some latitude because they did not know about the system, the same can not be said about the Ethiopian Air crew. They were supposed to be fully aware of the contents of the AD, and thus the existence of MCAS, the symptoms of a failure, and how to deal with it. Although they did eventually identify the problem, they failed to correctly execute the AD procedure to deal with it. To compound it, they then failed to 'fly the aeroplane', and allowed airspeed to build to the point where control and trim forces were completely unmanageable.
Re-certification has taken a long time due to both the sheer amount of work involved, and political interference in what should be a technical process.
The FAA would have needed to review all of the development documents to verify that no other change had managed to escape review (especially now that a 'hole' in the review process was positively identified).
Then the FAA also changed their view on acceptable flight test standards for runaway systems, which required a number of additional system changes from Boeing's side. (This is likely to be an ongoing problem, as all new (and possibly existing) aircraft will need to be tested to these new standards, and many will be found wanting.)
About the only silver lining is that the FAA did not ground the NGs (many of the newly identified issues likely affect the NG too) - that would have put a substantial crimp on the entire airline industry...