I was referring to the out-of-universe reason for why the battle between Mewtwo and Satoshi and Gou was conceived.
They literally said why. Mewtwo is a Pokemon so Go was going to battle to try and catch it, Mewtwo said it was the strongest Pokemon so Ash wanted to battle.On top of the Mewtwo's similiarity to Mew, it would make sense as shown why they ran into Mewtwo, or are you ignoring they went to find Mew and weren't looking for Mewtwo?
If you mean why did the episode exist to begin with? That's a question that can he asked about anything that I question the validity of why anyone would ask.
Why is Ash the main character?
Why did Ash travel with Misty, Brock, Tracy, May, Dawn, etc?
Why did Ash lose to Alain?
Why do they give Pokemon to characters just to release them?
Why did they give Ash Farfetch'd and Go Sobble in such a stupid illogical way while misleading the audience into thinking Ash was getting Sobble. In other words why did they feel Farfetch'd was a godd Galar Pokemon for Ash over a starter?
If the writers simply wanted Mewtwo to show off and impress the audience, I think they could've done so through a different scenario like I suggested before, rather than by having Mewtwo toss around Satoshi and Gou's Pokemon like rag dolls.
I fail to see why its impressive to instantaneously blast off Team Rocket when the protagonists already do that [if the plot doesn't demand a longer fight). Especially when the episode was clearly about Ash and Go and their goals a bit more than just only about Mewtwo and what Mewtwo can do.
I get the criticism of the lack of continuity I guess I'll never understand the criticism of the fight. Since any other powerful legendary Pokemon would've done the same kind of thing.
For example, Rayquaza would just use Hyper beam instead of shadow ball and while it wouldn't toss them around it would definitely blast them away.