What did Microslop change in Xbox One that prevented it from being exploited much in the same way? Afaik Xbone is still undefeated in terms of security, either because it's so good or because it's just uninteresting console to own

It has been defeated, but through hardware attacks (voltage glitching mostly). The author did an very interesting presentation about the process at reverseconf: https://www.youtube.com/watch?v=FTFn4UZsA5U&t