#1 Paving the way for Sami Zayn's return
Sami Zayn is Kevin Owens' best friend in WWE. Similar to how Owens went out due to injury, Sami Zayn also went out rather unceremoniously. Ever since moving to RAW, Zayn was also involved in some pathetic storylines against Braun Strowman and Bobby Lashley.
After all, who does not remember the segment involving Bobby Lashley's three "sisters". Zayn began his hiatus after being squashed by Bobby Lashley at Money in the Bank 2018.
Even though Sami Zayn and Kevin Owens are best friends, one fantastic thing about them is that they work amazingly as bitter enemies. Their feud in 2016 was nothing short of brilliant. Thus, if Sami Zayn were to return at Fastlane to prevent Kevin Owens from winning the WWE Championship, that would give a new dynamic to the Owens - Zayn feud.
Remember, all this time, Zayn has played the babyface and Owens has played the heel in their rivalry. But now, Owens may potentially play the babyface and Zayn could play the heel.