In-universe counterfactual: after escaping from Florum by the skin of their teeth, Maul and Savage are left to drift helplessly in the void in their dingy escape pod, rendered unconscious and now at death’s door.
However, whereas Pre Vizsla rescued them and Death Watch forged an alliance with the brothers IOTL, he overlooks them here, simply passing by and leaving the two to die, forgotten and alone. With the brothers dead and the Shadow Collective butterflied, how does galactic history proceed ITTL?
Maul is just a bit player in the grand scheme of things. His brother is barely that. I don't think their absence really changs anything about the way everything turns out, although random chance will lead to some different people dying and surviving, respectively. (Note that I can only really treat TCW as part of the Disney canon, into which it's been adopted. I never really consider it as part of the old EU.)
-- In general, Maul's shenanigans during the tail end of the Clone Wars ended up as a fairly minor distraction to the story's heroes (e.g. Obi-Wan and Ahsoka) and its villains (e.g. Palpatine and Doku), and to both the Republic and the CIS. Which means that if the brothers die in their pod, the net result cancels out, pretty much.
-- Without Maul, the Death Watch remains undivided, but also unsuccessful. He took control over a bunch of criminal organisations and used them in the campaign to allow Death Watch to seize power. Without him, Death Watch remains a thorn in the side of the Mandalorian government, but will presumably be unable to seize power. (On the plus side for them, their leader isn't killed, so they continue to exist as a cohesive entity.)
-- Without the Shadow Collective, the existing criminal organisations continue to exist. Within any given context, organised crime takes up as much "room" as it can (in that respect its tendency towards growth is very similar to that of...
government). This suggests that although the internal power dynamics will be different, the criminal underworld will be just as powerful, and will still profit in the same way from first the Clone Wars and then the inherently corrupt nature of the Empire.
-- The absence of the Shadow Collective prevents the situation that led Ahsoka back to Mandalore from ever occurring. Ahsoka doesn't lead Republic forces again, and doesn't fight alongside Bo-Katan, so they don't uddenly become all buddy-buddy and just remain enemies. Remaining in the underworld as a lone wolf character, Ahsoka presumably survives the events of Order 66 with greater ease, although this means Rex won't escape the effects of the mind control chip.
-- Maul isn't around to murder Satine Kryze. She seems as unlikely to really join the Empire as Bo-Katan, but she might be more like Bail Organa in just being all pacifist. This would make Mandalore less of a threat; if Palpatine just let Bail stay in charge of Alderaan for two decades, I don't see him randomly removing Satine from power, either. After all, it would presumably allow Death Watch to take charge, and they're actually less predictable!
-- Which means no carpet-nuking of Mandalore, while Death Watch remains as a united organisation... that may actually end up as an uneasy co-belligerent of the Rebels. (This earns the various splinter cells, such as the one that ends up taking in Din Djarin, won't come to exist. Most probably, Din is killed as a child. Or otherwise, he's raised by Death Watch itself.)
-- It also means Obi-Wan has a place to go to, which he might do. He might actually take Luke to Mandalore and hide him there. Remember, it's established that in Disney canon, Obi-Wan has no idea Anakin has survived until years later. And Anakin is the only one who might know about his connection to Satine, so going to Mandalore if Satine is still in charge there may seem like a smart move. (Ironically, the fact that Anakin is alive changes nothing, because Anakin would be utterly incapable of grasping that Obi-Wan might do this. Anakin won't even
think to look whether Obi-Wan is hiding with Satine.)
Things only really start to change once you get later on in the story. Without the Shadow Collective, Crimson Dawn remains a second-rate organisation, so the events of
Solo will certainly be prevented or at least play out differently. Maul won't be around to play the role he did in
Rebels, either, which at the very least means he doesn't blind Kanan. I think events in that series broadly turn out the same way without him, but I'm not sure about that. (And if we assume that Obi-Wan finds a place of hiding for himself and Luke on Mandalore rather than Tatooine, this obviously changes the events of ANH rather dramatically. But that's more of an interesting possibility to entertain.)
