Whats interesting to me in the Rebels episode 'Breaking Ranks' is two things in particular.
First, Ezra was stated to have been in the academy for WEEKS, living and training in the same building Kallus was working in. The way the cadets handed out datapads on the same floor as Kallus' office and to Kallus himself implies that he and Ezra probably crossed paths regularly and Kallus had NO IDEA.
It means Ezra also got to see how intensely workaholic Kallus is. 😅
Second, the decoder that he was trying to steal contained the location of a massive Kyber crystal.
This is one of the crystals intended to be used for the Death Star. Which was the project of Orson Krennic, funding rival of Thrawn, whom Kallus was not yet working under.
Kallus probably had not been told WHAT the crystal was for, but knew it was top secret (which is why he was trusted with the information).
There is so much fanfiction 'What if?' potential here!
What if Kallus had defected early and gave the code willingly? Would that have set back the Death Star plans and therefore the entire original trilogy timeline?
What if Kallus found out the significance of the stolen information after the war and has a massive whump moment over it? ("I had that information in MY HANDS. The LIVES I could have saved if I had acted on it...")
What if after it was stolen and while still an Imperial Kallus found out Saw Gerrera was ALSO after the information?
That particular crystal gets blown up pretty quickly, but I feel Kallus would have been able to help track down the other ones, if only he had known
Anyway, just my random analysis! 😁