There are several factors involved.

• The fundamental difference between a dedicated PDAF array made up of what is effectively one dimensional lines and an imaging sensor made up of sensels in two dimensions.
• The better signal-to-noise performance of modern sensors compared to those made a decade or more ago.
• The availability of faster, more powerful digital processing to interpret the data collected by the image sensor.

The first is a fundamental difference. Each dedicated detector in a PDAF array only measured along a straight line in a single direction. Image sensor based contrast detection can harness vertical and horizontal lines of sensels simultaneously. The image sensor used to perform AF is also exactly the same distance from the lens as the image sensor used to take the photo, because it's the same image sensor! PDAF arrays could have slightly closer or further optical distance away from the lens than the image sensor.

The better the SNR of the sensels used for AF, the faster they can return information just above the noise floor, the more accurate result they can return in the same amount of time, or a combination of both.

Processing power has exploded in cameras made in the last few years compared to those made even a decade ago. This allows faster computations of more data to be performed in a shorter time interval.

This also means that the benefit of a better AF with a fast lens no longer applies?

No, it just means slower apertures are now good enough where they were not good enough before. All other things being equal (say, the same lens wide open at f/2.8 compared to stopped down to f/16 during the time AF is performed), a lens with a wider aperture will always have an advantage when doing autofocus, regardless of whether it's using a dedicated PDAF array, sensor based contrast detection, or sensor based hybrid AF with some of the sensor's sensels partially masked to only detect light from one side or the other of the lens.