* The preference of well-off whites to pull the ladder up behind them;
* The preference of police unions to protect their members at all costs;
* The preference of the average non-black voter to not have to think about this crap.
I like that this is a pragmatic perspective that doesn't assume malicious intent behind most institutional racism (and tech debt, to continue the article's metaphor). People naturally act in their self-interest; it's not "I hate you" it's just "I'm not going to think about consequences when I optimize this solution for myself." While there are certainly many bad actors both in the creation and maintenance of our broken systems, IMO the vast majority of people are risk averse, passive participants in the status quo - i.e., falling into the third bucket. Even the more active participants in the first two buckets can justify their actions from inside their bubble; the horrible negative consequences are most visible only when placed in contrast to situations they often don't see.
Fortunately, people are recognizing the consequences of their actions - though not universally, and of course far too late to stop the death and marginalization of large numbers.
I hope it's a sign we're on the path to reduce or eliminate society's tech debt before the system crashes. Like all complex projects though, it needs sustained strong leadership.