What caused the change: Ronan killed Thanos after the Other.
This episode pays a lot of homage to Blade Runner (1982); the overall Future Noir aesthetic, the design of the Nova Corp patrol vehicles, the narration by Nebula (consistent with Deckard's controversial voice over added by the studio for the theatrical release of Blade Runner to hold the audience's hand - against Ridley Scott's wishes), and in the cityscape background as Nebula flies away from the opening crime scene you can see a pyramid shaped building like the Tyrell Corporation HQ central to the Blade Runner plot.
It makes sense that Nebula is still tricky and indirect; such skills helped her deal with the outlaws in the cosmos. She doesn't have much trust in others, but she takes vows very seriously.
Howard being on Xandar instead of the Collector's museum implies he was kidnapped at some point.
As Thanos was killed in 2014 and the present day is 2019, it makes the other histories of the heroes take a different course. 1) Thor and Loki can safely arrive on Earth with twice the surviving Asgardians. 2) As the Blip didn't happen, there wasn't a global shock to force the governments to repeal the Sokovia Accords, thus forcing the Avengers to remain shorthanded with just Iron Man, War Machine, Vision and Spider-Man; plus leaving Steve, Nat, Wanda, Sam, Clint, Hank and Janet on the run. 3) Monica Rambeau gets to say goodbye to her mother. 4) Strange isn't publicly recognized as a hero. 5) Mysterio can't trick Spider-Man into giving him access to E.D.I.T.H. 6) The Celestial will hatch from the Earth, as the Eternals were not inspired by the Battle of Earth to value humanity.