As previously reported, WWE has had plans to do Finn Balor vs. WWE Universal Champion Brock Lesnar at the Royal Rumble pay-per-view going back to November, despite the build to Braun Strowman vs. Lesnar, according to Dave Meltzer on Wrestling Observer Radio.
Vince McMahon reportedly started having second thoughts on Strowman vs. Lesnar coming out of Crown Jewel in November, according to Meltzer. The idea was to have Lesnar go over Strowman at the Rumble, building to Seth Rollins vs. Lesnar at WrestleMania 35. Vince felt at one point that Strowman vs. Lesnar was not a good idea because Strowman had started cooling off some. WWE had to do the injury angle with Strowman because he legitimately needed elbow surgery, but the feeling was that this hurt him some more. Vince also felt like they couldn't afford to beat Strowman again and their choices were to have Strowman win the title, which was not an option, have a bad finish in the match, but they didn't want to do that either, or not do the match at all, which is what they went with.
WWE continued to advertise Lesnar vs. Strowman to help move tickets, because this year's Rumble pay-per-view is taking place at a baseball stadium - Chase Field in Phoenix.
In regards to Strowman's future, PWInsider noted that the move was done to protect him. There was an internal feeling that another loss for Strowman would have hurt his momentum, and his long-term viability as a top star. There was also a feeling that Balor vs. Lesnar would make for a better story and a better match for the Rumble.
It's being reported that Strowman is still not 100% cleared for in-ring action, and there's no word yet on if he will be put in the 30-man Royal Rumble match, if he's cleared in time for the pay-per-view. Strowman's last real match was on the November 19, 2018 edition of RAW, where he was written out of storylines after an attack by Baron Corbin, Bobby Lashley and Drew McIntyre. He had elbow surgery the following week, and it was believed at the time that he would be ready to return to action by The Rumble.