I think Data East became Sega and then got bought by Stern. But I think I read somewhere that DE arose from the ashes of the old Stern run by Gary Stern's father, something like that.
First there was Bally and Williams and Gottlieb. Then Gottlieb dropped the ball when things went to steady state electronics so Williams took the lead. Williams bought out Bally and became the boss of pinball before giving up in 99. Why did they give up? Well, video games, home consoles, arcades closing, publicans preferring pool tables as no maintenance and more profit, games getting too good so new titles compete against old .......... bottom drops out of market, last ditch attempt is pinball2000 with RFM, a big hit, but the follow up SWE1 less so as film was **** and timing was off......... Stern was just the last man standing. Apparently the last Sega game, South Park, was so popular and successful that it also was a nail in the coffin of P2K.
Stern stayed afloat by cutting manufacturing costs and the games suffered. But the game had another cycle of popularity (still gathering momentum) driven by, I don't know, maybe digital pinball on computers. And the Internet. And IFPA and PAPA. And local leagues and the fact that all those young bucks playing pin when it was in its 90s heyday are now financially stable enough to spend a few grand on buying their childhood memories..
So competition arrived with JJP and Marsaplay and Heighway Pinball and independents doing smaller runs like Predator and Whoa Nellie's Juicy Melons and The Matrix and Captain Nemo. And Stern picked up the quality and is now the front runner and I bet Gary Stern prefers it that way to when he was churning out games that nobody wanted.
You should seek out a couple of long documentaries - Tilt, the Battle to Save Pinball; and Special When Lit