I think he is refering to those who invest/divest during the whale betting successfully. That magnifies the losses of the passive investors who stay invested throughout.
Yes exactly.
If people invest now, with a -3k profit: it will reduce everyone's profit. So mechs will have a harder time to recover from his loss if the profit comes from -3k to +4k. And then, at +4k, if people divested massively, and mechs stays there, and a whale comes and take 5k profit, he wil suffer a larger and bigger loss, because the casino would have less coins....