I do not know Gran, who hacked them.
Costing them 4 to 8 million dollars a day, still not all fixed, might take a year to get it all together.
Forbes article says this.......
Established ransomware groups ALPHV/Black Cat and Scattered Spider have both claimed responsibility for the attack. The incident was reportedly caused by hackers who impersonated an MGM employee they found on LinkedIn and called staff IT desks to gain entry to the MGM systems.