The answer to this question isn’t either one or the other; the answer is “both”. Susceptibility to addiction is genetic, and activation of that susceptibility, where it exists, is environmental.
Susceptibility to addiction is quite simple and specific. The adverse consequences of drinking makes 85% of the drinking population moderate their consumption, but 15% of the population continues to drink despite repeated bad outcomes. People that become alcoholics do not successfully learn from the bad consequences of drinking and we do not learn this because of an irregularity in the performance of a part of the brain known as the amygdala. This irregularity is of genetic origin meaning that we are born with it, we do not choose it. This susceptibility involves a concurrence of several genes that are a perfectly common combination across society and if they occur in our parents then we are likely to inherit them. Susceptibility to addiction can be inherited but it can also occur quite routinely through natural variability.
Drinking regularly, for whatever reason, will activate this susceptibility where it exists. Addiction will form in people that have this susceptibility AND drink regularly, but once initiated then alcoholism no longer needs that original stimulus to worsen. Addiction forms into a self-reinforcing feedback loop that once formed will continue to strengthen itself and removing the original stimulus does not stop its progression. Whether the original cause of drinking was; peer pressure, familial setting, or escape from some trauma or other distress, this does not alter the course of addiction… once begun it will progress regardless of the original circumstance. Once a fire has been lit then the original spark is no longer needed for the fire to grow and alcoholism progresses in exactly the same way. But if the fire is put out then the original spark needs to also be extinguished or it may re-light the fire. Enduring distress (e.g. suffering the trauma of some type of abuse) does not progress our addiction but it may cause relapse if it is left unresolved. If there is some deep trauma that may cause relapse then we need to get this treated as an independent issue if we are to achieve long-term sobriety.
Addiction, once established, has nothing to do with other people or events, it is only about us. We have activated our susceptibility and once activated it strengthens without limit. That susceptibility is genetic and cannot be changed. We did not choose this vulnerability, we were born with it, and it will never go away. We never recover the means to control alcohol because the deeper truth is that we never had that control in the first place. Nor do we do not alter the course of addiction by changing the circumstances that activated it because once addiction is engaged then the original cause is redundant. Finding others to blame does not help us in any way whatsoever, in fact it is damaging to our recovery because it distracts us from recognising that the problem lies within us. We are where the problem lies, we are the ones that we have to work on, and we are the only ones that can do so.