From what I have read, the separation policy was a direct result of a judicial ruling that basically said you had to release minors immediately. The parent would bring their children (or perhaps other minors claiming they were their children) and then would claim asylum. To keep the families to together, the accompanying parent would be released to stop the separation from their children. They would be assigned a case number and asked to stay in contact and asked to come back later for a hearing. This is what Trump meant by catch and release. The number of people coming in and taking advantage of this started to soar in 2018. To try to combat this, the Trump administration started to separate the children from their parents. This was an attempt to stop the migrants from using the loop hole to get into the US. I am not sure of the best approach, as both letting them go and separating families are bad policies.
But, one must remember, at any time I believe the parents could agree to be deported and leave with their family. I guess the belief is that if you are looking at death or severe persecution, the separation is worth it. If you are doing this for other reasons, it might discourage you.
Lot of issues here.