NJPW's incursion onto U.S. Soil
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Bullet Club's rise as the only foreign-led stable in New Japan opened a completely different avenue for wrestlers and fans. Frustrated with management, AJ Styles left Impact Wrestling with whom he'd been synonymous with for ages. He joined New Japan on a whim, becoming the next big thing for the Bullet Club faction.
Even then New Japan wasn't ready, Styles brought with him a decent set of eyeball and exposure to the brand. Then the ELITE took it on a whole other level. By then WWE might not have had a legit competition for their brand (they still really don't) but New Japan had a new set of fans mired in the wrestling world.
Their strong style form caught attention and an incursion into American shores made possible. Coupled with their partnership with Ring of Honor and other rising independent the face of wrestling was going through a transformation. ALL IN, a conglomerate of all this talent and push becoming the resultant final explosion.