I don't think the DA is racist, just sometimes a little careless in what they say and do. Their cabinet ministers are doing a good job and I think many DA-sceptic people will change their minds about them
A theory: the DA's growth has been a process of gaining soft (less committed) support, some of which it has consolidated as core (more committed) support. I think its soft support is at a low right now. This is good them, because they are not in danger of losing many votes, but with the right...
I think Maimane was a symptom, not a cause. After consolidating the former NNP vote, DP/DA tried to right itself by edging left again and this included absorbing the Independent Democrats and promoting Maimane. They were trying to be too many things to too many people. Zille realised this, but...