Your Question: "If the wrathful, jealous, and genocidal Old Testament God existed do you really think he would allow religions that worship idols and other gods to exist, let alone flourish for thousands of years? I think there would be far fewer religions and many more followers of abrahamic religions in the world if God as described in the OT actually existed."
Should we assume the former by what we see in the latter without considering them together? With so much evil flourishing in the world and falsity prevailing among the many, would it not be more fascinating to ponder why there is any good in this world at all - if even reflected in just a few? If the nature of the earth is bent on violence and involuntary suffering, why not wonder about the origin (and persistence) of peace and/or philanthropy and/or loving self-sacrifice?
And considering that, would it not be within reason (indeed one higher than ours) that this almighty G-d, jealous over His own creation, having demonstrated His powerful wrath in a few at the beginning, might tolerate the wrath of many later to demonstrate His good will and love for all in the end?
It is to our great fortune that our G-d is Who He is, and to His great honor that He hides His greatness from the proud of this world - that mankind's own true pride might be perfected in His greatness for eternity (though it be hidden for a time in our shame).
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In my own pride i once said "there is no G-d" - now humbled, i wonder: how could i have relied only on things of flesh i could see with my eyes and hear with my ears to reason about One unseen Who is spirit? And having done so and (logically) not arrived at the knowledge of Him and His distinguished Spirit, why then did i not stop at my ignorance? Rather, adding foolishness to my lack of understanding, i proceeded to mock Him and His instruction in the law, vocally denying His justice and rejecting the righteousness of His judgments - all the while thinking myself wise in condemning the Judge, Who had yet to even execute His judgment fully...(and before which i couldn't stand for a moment)
how could i have known He had intended good by extending His patience? how could i have known it was mercy and not weakness that held His power beyond our sight? how could i have ever imagined the overwhelming goodness of the surprise awaiting those who seek Him with all their heart and the beauty of His countenance upon those who call on Him directly. who would have thought it? and who would believe a human report? If you will not accept my testimony of His goodness, on what basis can one accept any other testimony of His non-goodness?
"Out of the depths I cried to the Lord, and from His high place He heard and had mercy on me."
"Taste and see that the Lord is good."