seperate HEP generator trend

MPIs and the F59PHI and some F40PHs all have separate HEP generators. Separate HEP generators seemed to become the standard in the 1990s and 2000s. In the 2010s, why has this trend reversed itself with the HSP46 and F125 and Siemens Charger all supplying HEP from the prime mover?

For the F125 and Charger, a lot has to do with weight. In order to reach 125MPH and not do damage to the track at that speed, it is advantageous to be as light as possible. Lighter locomotives also ride better with less sway at higher speeds. I'm not sure why the decision was made on the HSP46.

The generators were installed on locomotives designed for commuter service where keeping the prime mover at the equivalent of notch 4 or higher even at idle was bad for noise and exhaust emissions. Long distance power has less of a problem with this.

also due to HEP now supplied by inverter it does no longer require the prime mover to run at 900 rpm.
todays AC traction locomotives with HEP inverter will run anywhere from 580 rpm to 900 rpm depending on demand not just RPM to keep frequency at 60 Hz.