You won't seek gambling if you're in trauma, and if you're thinking that probability gambling is the effect of trauma; well I don't think so. Probably you're in trauma after you've been addicted to a certain thing not just with gambling but also with another matters. So being into traumatic experience is a situations that you won't hope that it will not happen again, but still lingered in our mind. Mostly, people who undergo this type of scenario will have anxieties and become stressed, thinking that they won't recover after such those bad experiences on gambling addiction.
It's not that you start gambling right after you've experiences trauma, you start engaging in addictive and destructive behaviors after a while.
People do that to cope with the general bad feelings that remain after the trauma.
It's actually something that's pretty well researched, so you're just completely wrong with your statement there.
Here's one research paper that tasks specifically of the prevalence of gambling addiction after experiencing childhood trauma.
The study was done on twins.
https://journals.lww.com/jonmd/Abstract/2007/01000/Association_Between_Exposure_to_Childhood_and.12.aspxSummary of the study:
The present study seeks to estimate the strength of the association between exposure to lifetime traumatic events and gambling problems while accounting for the potential contribution of psychiatric disorders, genetic factors, and family environmental influences.