I could be talking out of my rear but here it goes... Cedar Fair (now Six Flags) is a publicly traded company with a duty to provide returns to its shareholders. It is not going to "cut ties" with a manufacturer because the manufacturer's coasters that pushed the envelope at Cedar Fair's request had issues. Another thing to keep in mind, when a manufacturer creates a ride, it almost certainly is done jointly with the park and it is not a manufacturer only project. Cedar Fair/Kings Dominion almost certainly wanted the coaster to be that intense with the blackout inducing first turn. Case in point, the trim was added *after* the ride opened. CF/KD were aware of its forces when it opened yet still opened it without the trim on the first drop. It opened that way presumably based on the success of Maverick with its intensity... Not enough people talk about the G-force on the turn over the lake after the 2nd launch. Either way, it was not like Intamin said here is the coaster and good luck to Cedar Fair and Kings Dominion. It was almost certainly a joint effort to deliver that coaster in its original form.
What Cedar Fair has done is placed a higher premium on reliability, maintenance ease and capacity. This becomes quite obvious when looking at its large scale coaster installations post 2010. I would say Cedar Fair has installed 17 large scale unique thrill coasters after 2010 with it looking like 2 more in 2025, so 19. The breakdown by manufacturer is as follows:
B&M - 9 (Leviathan, GateKeeper, Banshee, Fury 325, Valravn, Yukon Striker, Orion, Iron Menance, Kings Dominion 2025 Coaster)
GCI - 3 (Gold Striker, Mystic Timbers, Zambezi Zinger)
RMC - 3 (Twisted Timbers, RailBlazer, Steel Vengeance)
Gerstlauer - 1 (HangTime)
Mack - 1 (Copperhead Strike)
Zamperla - 1 (Top Thrill 2)
Premier (Presumed) - 1 (Canada's Wonderland 2025 Coaster)
By the way, the amount of times Cedar Fair uses Strike/Striker in coaster names is bothersome, ha.
The next point is that Intamin and RMC have not exactly had light workloads in recent years. That means that the manufacturers can charge a premium price and or be unable to complete deliveries by the time a park/chain desires. By my count, Intamin has delivered 77 coasters since 2010 and RMC has delivered 10 coasters since 2018. And those company's aren't slowing down. For comparison, since 2010, B&M has delivered 52, GCI with 19. I am aware this goes beyond the large scale thrill coaster discussion from the prior paragraph.
The final point is that Intamin's current "strength" is its LSM launch coasters and its hyper coasters. From 2011 through 2024, Cedar Fair only installed 5 coasters in that vein if you include the B&M GIga's. There have not been a lot of opportunities for models that are Intamin's strength. But we do keep hearing the rumors that Cedar Fair folks were blown away by VelociCoaster so we can hope that eventually we see a trend of LSM launch coasters showing up at parks.
Finally, it is possible that Cedar Fair did pump the brakes on using Intamin (and RMC) due to potential relationship fatigue. Professional relationship fatigue is a real thing but that is far different than cutting ties.