If things had played out like the game in his past life with Mycroft and the rest of the galaxy, both scenarios would have been identical before Starfall Year 855.
The difference between the two worlds was probably the innumerable players in his past life, while this Mycroft world had a certain count named Joshua van Radcliffe who used the system to level up meteorically, rising to Legend within a brief few years.
When he compared the two timelines, Joshua was sure that he did not change the world much before even after he killed Nono, the Black Dragon and stopped the Abyssal draconic armies.
It was in the end, when he changed the tides in the Battle of the Holy Mountain, killing the leader of the Pestilence Cult, reigniting Mycroft's Flame, heading to Stellaris to protect the Midgardians from the Void Mother, as well as restoring life Kronos… those were the acts that changed the galaxy drastically, providing Joshua with many precious data and clues.
