There is very strong evidence that it is genetic. The genes identified so far point to the immune system cells being unable to identify and/or kill candida as well as in people who are not genetically susceptible to it.
The genetic link does not change the fact is that for almost all people if they had never in their life received Antibiotics , they would be very unlikely to get it, as it was rare 100 years ago - and if even they did get it in some other way (e.g. sexua| transmission) it would be a much much milder case.
I have seen no real evidence that its caused by allergy to yeast. In fact the opposite is true. When animals were infected with candida in their intestines by feeding them Antibiotics , they developed new allergies to stuff they were not previously allergic to (that would include mold, yeast, pet dander etc). The animals that were given placebo rather than Antibiotics did not get allergies, even if they were made to breath the same allergens.