Disease is more complex than just Candida, most people I know can't hold good intestinal flora due to ileum issues. So if you ileum dysfunctions then you get a Candida issue again.
PH is another, lack of sulfur in the diet (MSM) allow intercellular issues that may take years to clear. So you run the cycle of re-establishing good bacteria in your gut but other places haven’t had time to kill off the bacteria.
Killer (bad) bacteria due to “the quacks” overuse of Antibiotics is another, and of course parasites bring their own brand of candida/yeast/bacterium…