They might not be, but there are limited reasons to why people lose the care of their children.
There could be extreme violence in the relationship, which could significantly put the baby at risk
There could be significant MH issues which mean that the parents are so ill that they're not able to keep the baby safe. Their MH could cause them to be violent or have episodes where they act dangerously or neglect the child.
There could be substance abuse issues, and if so, it might or might not lead to violence but if a serious addiction, it usually leads to neglect of children
There very well could be a combination of factors
Their track record of leaving accommodation in a terrible state and with unpaid rent suggests chaotic and unpredictable behaviour, despite her money, so she is either very ill and/or abusing substances of some sort.