Yikes, I know far more about Babylon 5 than anyone needs to!
There was a strong chance the series would be cancelled as the end of season 4, so J Michael Straczinski tried to wrap everything up into a satisfactory ending. He therefore didn't progress any of the storylines leading to the telepath 'war' and the resolution of the vorlons v the shadows felt a bit rushed, but this was doubtless the best he could do.
Then it was recommissioned for the planned 5th season, but half of the arc intended for that season had already been completed in season 4.
Meantime the lassie playing Ivanova had decided to leave. So the telepath storyline had to be rejigged with Lyta taking her place. This badly affected the story, as Ivanova's motivation for involvement would have been her suspicion of Psi-Corp and the loss of Marcus, who sacrificed himself to save her at the end of season 4. Lyta getting involved in what was basically a telepath cult lacked these drivers and seemed very 'off'.
I'd have loved to see the original intentions of seasons 4 and 5 followed through - though at least it did get a proper ending.