My personal sign is when you start seeing awkward collaborations start cropping up. One time when I was thrifting, I picked up a graphic novel that had the Justice League, team with the Power Rangers of all things. I glimpsed into what the plot was about out of morbid curiosity and it was just a plain generic time and dimension thing.
Nothing ever connected between the teams at all. DC Comics, while fledgling at times with how they go about their series and movies, still have far more relevance than Power Rangers do. I think the Power Rangers are just grasping at straws to keep being relevant when people have largely moved on from them.
And honestly, when they spend the last two episodes shoehorning all of those loose ends in as if it were somehow the plan all along, but in the process they create plot holes.
For example, Season 2 of Arcane having Heimerdinger being suddenly onboard for the dangerous time travel experiments just so they can have Ekko ready in time for the finale, but they also place a bunch of random restrictions on his powers such that they cannot actually alter the past but they somehow can alter the flow of fights in the present. That whole season was terrible, tbh, none of it made any sense they just wanted to rapidly take the characters from where they were in season 1 to what they are ingame with little to no explanations of how or why.
Reading this wrong without having seen game of thrones confused me.
Until I realised I didn’t read the words “of Arcane”
As I see it, Heimerdinger was ready to give up, when he was removed from the PiltoverdCouncil by Jayce, his former pupil. He tried previously to dissuade Jayce from using Hextech like this.
Then he found Ekko creating a community in Zaun with an inspiring ingenuity despite pretty much everything else happening, so Heimerdinger decided stayed and helped out while teaching Ekko on how to improve on his designs. Heimerdinger wants to improve the world after all - but safely - and sees his opportunity here.
Then in season 2 they wind up in alternative dimensions due to Hexcore shenanigans, because Heimerdinger wants to help Ekko sustain his community. Jayce ends up in over where the “final battle” already happened. Heimerdinger lands in one where Hextech apparently does not exist at all and the city is better off because of it missing. One where Heimerdinger himself can probably be more relaxed as he has more time for his stuff and has to deal less with politics and betrayal.
Ekko arives 3 years later. And Ekko wants to go back no matter the cost. And this puts Heimerdinger in a pickle: the last time he tried to dissuade his his pupil the results were catastrophic. Ekko would have worked it alone (or would probably have roped in Powder) endangering not only himself but atleast Powder, probably even the Zaun/Piltover (mind you, Ekkos knowledge about Hextech is very limited, while Heimerdinger oversaw the research most of the time - and Hex is notoriously unstable).
So to protect the timeline/city/Powder/peace he liked as well as helping Ekko get back to his community the reasonable conclusion would be to help despite not being keen of the idea. The ~4 second limit of the Z-Drive comes from the instability of the Hexshards. Any longer and it goes boom, potentially killing people around. And this limit is what he uses to break Victors mask in the end for Jayce to intervene.