In a recent edition of the Wrestling Observer Radio, Dave Meltzer indicated that Braun Strowman was pulled from the WrestleMania 34 singles match with WWE Intercontinental Champion The Miz due to concern over the Roman Reigns vs. WWE Universal Champion Brock Lesnar main event.
Strowman was reportedly pulled from the singles match with The Miz because officials felt that it was important to have some sort of back-up plan for the Lesnar/ Reigns main event, in case damaging evidence against Reigns may come out of the investigation that filmmaker Jon Bravo is doing.
It was previously reported that Reigns was identified and included in a steroid drug ring by jailed steroids dealer Richard Rodriguez, along with actors Mark Wahlberg and Josh Duhamel. Reigns has denied any accusations but Bravo recently indicated that his report on WWE is complete, and that he has evidence on a former WWE Legend placing more than $140,000 in orders with Wellness Fitness Nutrition, which was ran by Rodriguez. Bravo also said that the report will contain evidence on Reigns and other former & current WWE Superstars. Bravo says that his findings will be released soon.

There is no word yet on what might be planned for Strowman at WrestleMania but it could be some sort of a throw-away match. Meltzer also speculated that Braun could end up facing Elias or Samoa Joe, if Joe is able to return. WWE could also always add Strowman to the Reigns vs. Lesnar match to make it a Triple Threat but as of right now there are no plans or rumors of that match happening.
It was previously indicated that WrestleMania 34 will see The Miz defend his Intercontinental Title against Seth Rollins and Finn Balor in a Triple Threat Match. Justin Barrasso of Sports Illustrated recently reported that the Intercontinental Match at WrestleMania 34 will be a Fatal 5 Way Match with The Miz defending his title against Seth Rollins, Finn Balor, Elias and Braun Strowman, but as of right now that is said to only be a rumor.
Source: F4WOnline