Reality is much more nuanced, and the article actually does a good job of detailing that.
In some sense this all started from the very beginning, from when Alzheimer's disease (AD) was first described: In 1911, Alois Alzheimer found plaques in his dementia patient's brain. [0] These plaques are what researchers would focus on for more than the next 100 years.
Much later, the protein giving rise to the plaques (APP) was discovered and there seemed to be good evidence for a causal role: Mice with mutated APP developed AD.
Quoting the article:
"""
By the mid-1990s, a now-defunct San Francisco biotechnology company, Athena Neurosciences, created the first genetically engineered mice with a mutated, amyloid-producing human gene. The animals’ brains filled with amyloid plaques, and their memories were destroyed. The mice were hailed as a “model for testing therapeutic [Alzheimer’s] drugs”
"""
So we should really take this story as a cautionary tale. There was, however, no conspiracy or "cabal". These were simply people who were convinced they were on the right track. In a way, they were, since hereditary Alzheimer's is caused by APP mutations, it just turns out that this isn't as important as other ways of developing the disease.