Lord Beerus wrote:Piccolo just states that Goku isn't fighting for him and that he's bearing the hopes of his allies. Not that simply because he has friend and Jiren doesn't. And Piccolo was more or less insulting Belmound for not realizing how Goku was able to improve himself in battle while using Ultra Insticnt, while Piccolo was able to back in Episode 110. Despite the fact that Belmound is Hakaishin and has knowledge of the technique, while Piccolo, a mere more who had no idea what Ultra Instinct, was able to pick up on the subtle idiosyncrasies related to Goku's evolution in combat while using Ultra Instinct.
That statement in itself continues the trend of the Universe 7 fighters talking to the Gods of Universe 11 from the previous episode (Episode 129) where Belmound arrogantly believed that Universe 11 were going to win and talked down the idea of Goku mastering Ultra Instinct and surpassing Jiren. Only for Vegeta to wonderfully rebut him with the statement of how the Saiyans of the Tournament Of Power broke through their limits time and time again.
Also, Goku didn't just immediately overpower Jiren. The battle still remained incredibly even despite Goku's increase in speed (not power), until the very end.
No, Goku's UI was already mastered, back in 110, Goku was growing to master it, big difference. Goku's speed increased suddenly and Belmound wanted to know why. It was because of his friends. Did you forget Belmound was already schooled by Vegeta on saiyan growth? This is when Goku still had a chance to improve by mastering UI. Belmound now wants to know what's the deal NOW?
Piccolo's comment does not provide an context of Goku's speed increasing just because of his allies. Piccolo states that Goku is carrying the responsibility of saving their fucking universe from being erased. It has nothing to with special ties or "friendship". It's simply the fact that one man (Goku) still retains the resolve to carry on fighting knowing full well what is at stake and taking into account what is happening with his battle against Jiren.
As far as the cast were concerned, Goku was the only thing preventing Universe 7 from being wiped from existence, so naturally they put all their faith in Goku to win, not because of friendship, because they don't want to be erased by Zeno(s). Goku is aware of this, and so is Piccolo.
And Piccolo is also aware that, even in extreme circumstances where billions of lives are on the line, Goku can act selfish and be in it for himself (Cell Games), hence why he remarks that Goku isn't only fighting for himself, prior to stating that Goku is bearing the hopes of Universe 7 in a battle that determine whether Universe 7 lives or doesn't.
If Piccolo had stated that Goku had special ties, or explicitly stated that Goku has allies and Jiren doesn't, then I'd side with you argument. But that's not the case. I don't know how faith in a single person to prevent universal destruction can be misconstrued as simply the "power of friendship".
With regards to how Goku's speed increased -- even though it made no difference -- it ties back to what Vegeta stated in Episode 129: the Saiyans find ways to break through their limits time and time again. Goku found a way to somewhat improve on the complete Ultra Instinct ability.