Is There A Single Cause That Led To Every Conditioned Phenomena?

I guess not. There must have been multiple causes that led to not a single but multiple results as well.

Am I wrong?

You are correct.
Dispeller of Delusion p.181

  1. For here there is no single nor multiple fruit of any kind
    from a single cause, nor is there a single [fruit] from multiple causes,
    but only multiple [fruit] from multiple causes. Thus from the multiple causes, called temperature, earth, seed and moisture, fruit
    called a shoot having visible form, smell, taste, etc. is found to
    arise. But |148| one representative cause and fruit given thus: “With
    ignorance as condition formations [arise], with formations as condition consciousness” has a meaning and it has a purpose. For the
    Blessed One uses one representative cause and fruit when it is
    suitable for elegance in teaching and to suit [the inclinations of]
    those susceptible to being taught. [And he does so] in some instances
    because it is a basic factor,38
    in some instances because of obviousness and in some instances because of being not shared.
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