Because it did’t want to repeat past Mistakes>Paragraph 2
Because its a Mew, Mew can Transform and do mental jiggery pokery. Think Mewtwo at the end of the first movie, that isn’t time travel its a memory wipe snd manipulation. If you mean age, anime established in its second movie Mew is biologically immortal, it doesn’t age so it could have been active the whole 1000 years. And PMD borrows from all sources.>Paragraph 3
You answer your own question. The past Mew is only referenced by the partner not the new mew, we know past Mew is active in the game as it does things like wipe the players events. At the end credits the partner identifies itself as Mew and that it remembers everything, but it also says it remembers being the partner and wants to be the partner. It vanishes, player meets Numew who makes no reference to past Mew, its its own Mew but the player notices aspects of the partner in it, Mew feints, player is given their ultimatum, the partner returns but nolonger references past Mew in any way. Its at this point past Mew can be said to be gone.>>40445567
Agreed especially since it seems they actually did repeat the same actions anyway going straight for the waters Nuzleaf needed the player to access as well and nearly blowing their mission. My pure head canon excuse, they fought fire with fire in the past fighting with anger and hate which is why Dark Matter endured, or Mew at least since Dark Matter seemed fixed on it and them on Dark Matter being, “The only one who could end it”.