One of the two likeliest motivators could easily be the termination of the clone army. I have little doubt that we will eventually learn why Rex, with Gregor now in tow, fled to this desolate world and allowed the likes of Ezra Bridger, Hera Syndulla, Kanan Jarrus, and Ahsoka to fight the good fight on their own. Especially after how active he appears in Bad Batch.
This still begs the question, what drove these once proud soldiers to this non-descript retirement? While clones obviously age at nearly double the rate of a normal human, it seems odd that Rex of all clones would abandon the galaxy to Imperial subjugation. The Empire seems content to let them drive their heavily modified AT-TE around on Seelos and only comes after them after their connection to the Jedi is revealed. In Rebels, we see Captain Rex, Gregor, and Wolffe enjoying their retirement as old war veterans often do: fishing. RELATED: ‘The Bad Batch’ Has Marked The End Of This Era In ‘Star Wars’ However, with the continued transition from clone to stormie, it seems only a matter of time before Jango Fett's clones are rendered obsolete and disposed of.
The Empire clearly still values the clones for their military ability and obedience, as seen by their presence on the Venator-class Star Destroyer that rained destruction on their homeworld and obliterated Tipoca.
With Se being taken into Imperial custody shortly after this scene, the fate of these young troopers, and clones in general, is left very much in limbo. These early stormtroopers are plentiful if not particularly talented, as indicated by clone commando Gregor in episode 14, "War Mantle." In some of the final moments of Tipoca City, we see a column of young clone cadets being escorted to their new assignment by Chief Scientist, Nala Se. Much of the first season of the show dealt with the transition from Kaminoan-bred clone troopers, to Imperial recruited TK troopers.