According to Ra’s, they should work together because of a shared investment in Bruce Wayne as well as Gotham City.
Jeremiah was left with just about nothing… until Ra’s al Ghul turned up to offer his help.
The good guys scored some wins on Jeremiah in “One Bad Day.”
These are the two arguably most formidable living villains on Gotham; if there’s a way to take destroy Gotham and turn Bruce into the future Batman, these two can do it together.