NCR is at fault here for the timetable like this. For operational ease, Patna Rajdhani is part of the Rajdhani lineup that runs between Delhi to DDU back to back. In this lineup, Patna Rajdhani is at the back, still it is very early departure for the Patna Rajdhani.
For timetable improvements, they can run this Rajdhani between ANVT-JYG/BGP Garib Rath and Prayagraj Express. This way, both Rajdhani and Sampoorna Kranti from Delhi to Patna get similar timings.