"why would a couple of people want to go to a township at night when tourists get warned of the dangers of going there at night"
To see the "real" South Africa?
There are now plenty of tours of some townships and some of them also have tourists staying there overnight. The image being presented, as I've said above, is that this is quite secure as the residents protect the tourists knowing that if any harm came to them it would shatter their income.
And the husband says that the plan was just to drive through the township.
So it does sound reasonably plausible and I can see why it could have happened.
"don't think the taxi driver would have suggested it."
I don't think anyone is suggesting that he did, it was apparently the Wife's idea.
I'm not making any comment on who is guilty for all of this.
What I am saying that it's plausible that they did just decide to go and visit, that the taxi driver could lie to get a plea bargain and that there are a lot of people who want this to be seen as a "simple" murder of a wife by her husband.