What are reason's men cheat?

I have been through this situation in every relationship I have been in ( all long term) I have gotten feedback from ex's to try to help me understand one said "You made me suspect you so I reacted" which is obviously projecting onto me from insecurity, one said "I am insecure" plain and simple but did not really ever do any positive life changes to rectify the problem. One person was a compulsive liar and just denied it through and through but it became obvious to me they seeked validation. So my question is what are reasons men have cheated?
What are reasons men cheat?
What are reason's men cheat?
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