This does not prove that it happened that way, nor can this be replicated in any experiment.
That is, they cannot take a cell without a Krebs cycle, give it the initial starting conditions, then wait through several generations and then end up with a cell with a Krebs cycle. The term "opportunism" in this case is simply a synonym for "something magic happens".
“They explain how it may possibly have happened.”
Hey, that’s all it takes for the evolutionists to declare victory. Just the ‘possibility’ is all they care about.