Initially, Apple had standard, 5V 1A chargers.
Then they've made "Fast" chargers, which were delivering 2.1A at 5 volts.
However, while Apple was stuck at 10W charging, in the android world, several charging standards emerged, most common and popular to be Quallcom "Quick Charge", which was delivering up to 18W into phone. However, further improvements of that protocol made more into power efficiency, but not into power amount. So other companies started to develop their own solutions - Samsung, Huawei, Oppo, all have made their own standards. So it was really crowded there, and big guys decided to settle, so USB PD was born.
But USB PD does not means that you will get fast charge all the time. This is just standard, which has different "power levels", so it is quite possible for charger to be USB PD compliant, but deliver only 1 amp into load at 5V. To make things even worse, some companies developed their own extensions, which run over USB PD, and are not fully compatible. For example, Samsung developed PPS protocol, which runs over the USB PD protocol, but requires compatible charger, so even if you have USB PD charger, to charge the modern samsung phones, it should also have PPS support. So, things are really complicated.