First of all, the question has a twist, MLM never fail peoples fails or left.
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Because MLM is a number game and its very difficult to hold public in the same interest for a long period, Public change their mindset according to time and market follows,
While group disturbs or move due to their interest in change in the latest technology or high yield best income source, they move own.
Indirectly you can say MLM failed, but affiliate marketing is different from MLM, Here in Affiliate marketing you will continuing life long because its depend on only you and your activity if you are active with a good product and that product available for sale or brand have produced different products.