At the heart of this is just basic fairness and sticking to what was agreed on.
Betfury accepted Dplay’s bets in good faith. Those bets were already well on their way to winning, some even had 3 out of 4 legs already settled in his favor. That’s a huge trust issue.
Yeah, casinos technically have the right to void bets, but using that power after a bet is clearly winning just feels shady. It basically sends the message: "We’ll take your money when you lose, but cancel when you win." That’s not how fair play works.