Try playing the major mods out there if you, like me, desires the Seleucids to be the superpower they actually were: the most powerful empire in the known world at the time. Most major/large mods really put their efforts into this particular case of Ptolemaic unhistorical/annoying success in crushing their supposedly superior neighbors, who, in history, successfully drove the Ptolemaic dynasty out of Palestine and Salamis, and even threaten, several times, with real possibility of success, to conquer Egypt. The Seleucid rise to power, albeit going through several huge setbacks, finally ended at Magnesia, by Rome's hand, who viewed them as the eastern superpower who was a serious threat.

In game it's just Ptolemaics beat out poor Seleucids, indeed, I would like you to post a screenshot about this campaign, if you really don't interfere in the early wars of the east when the Seleucids were often wiped out among the AI.