Incoherence can actually be a surprisingly effective communication strategy - if what you want to communicate is 'I'm someone who agrees with you about the right things', rather than communicating actual information, facts or logic. It's similar to Banham statements or astrology in the way it makes the listener create the content.
If you make a lot of quite general, unconnected statements - and say them in a way that suggests they are connected - the listener inserts their own links. If you don't finish your sentences, the listener makes up the end of the sentences and extrapolates what point you making.
And because they have made them up, from their own beliefs, knowledge and biases, these links and points tend to agree with what the listener themselves would say.
It doesn't work on everyone. If you are very interested in the topic so are listening carefully and analysing, or if you have a particularly detailed and informed view on the matter, you are likely to see the holes. If you have an existing antipathy to the speaker then you may do the same filling in process, but fill the gaps with things you disagree with.
But it works on a lot of people a lot of the time.
It's a manipulative strategy that it pays to be aware of. Although it can be tricky sometimes to tell the difference between those who are incoherent to manipulate, and those who are just talking nonsense because their thought processes are complete mess. There's often a certain amount of overlap.