#2 The star power

Love it or not, Roman Reigns is, without an iota of doubt, WWE's biggest full-time Superstar on the roster. Similarly, The Undertaker is one of WWE's biggest stars of all time. No other matches during the event possess better star power.
Moreover, The Undertaker is on a streak. After his Casket Match against Rusev at the Greatest Royal Rumble in Jeddah, Saudi Arabia, The Phenom has only contested in the main events of WWE PPVs.
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The Undertaker faced Triple H in the main event of Super Show-Down in Melbourne, Australia. He teamed up with his "brother" Kane to take on DX in the main event of Crown Jewel in Riyadh, Saudi Arabia, and quite recently the Deadman faced Goldberg in the main event of Super Showdown in Jeddah. WWE would be looking forward to using the Deadman as the main event attraction from now on.