#4. His health

Roman Reigns announced in late October last year that he was battling leukemia. It came as a shock to everybody and as mentioned earlier, the general consensus was that Reigns would mostly return to the ring around January 2020.
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WWE perhaps assumed the same and came up with a plan to keep going without him despite Reigns being a very integral figure to WWE programming. Unfortunately, due to the nature of leukemia, Reigns knows that there's a very high chance of a relapse and his health going down the drain.
Out of pure respect for his physical well-being, he likely knows that it's going to be difficult to push past two years on the road and in the ring. That's why he most likely feels that for his health, a two-year period in WWE to do all he can would be good.
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