Jonathan discusses why The General Theory was so successful here. As I understand him, he's saying that it was successful because it adequately critiqued what Jonathan calls "Marshallian" economics. Keynes was fond of Marshall, and so I think you'll be more likely to find Keynesians call it "Classical" economics. One of Jonathan's points seems to be that the Austrians never were Marshallians and this became especially clear only after Keynes successfully displaced Marshallian economics.
Towards the end he talks about what Austrians ought to do to assert their "supremacy". My position, of course, is that they have no such "supremacy", so they ought to be strategic. There are good ideas that Austrians can contribute. ABCT, I think, has a lot of potential in the mainstream as one of many macroeconomic mechanisms worthy of study. Believe it or not, I'm actually warming to Austrian views on inter-subjective utility comparisons. My position used to be that making these inter-subjective comparisons was a justifiable modeling assumption that didn't do all that much harm. After all - we're really mostly dealing with marginal utility, so Austrian hand-wringing about whether total utility comparisons can be made always seemed beside the point. Lately, though, I've been so frustrated with implicit conflations of clearing markets and "ideal" outcomes that I'm beginning to wonder whether the whole welfare economics outlook that people carry over from micro is doing more harm than good.
Regardless, the point is Austrians have good things to bring to the conversation and I support that enthusiastically. I don't agree that they have anything that would displace the Keynesian paradigm that we're in. Some day I'm sure the paradigm will shift, and I hope I'm not so old and crusty at that point that I miss it. I don't think the Austrians will bring that about.
Ultimately, Jonathan rejects this line that Keynes succeeded because he was good for politicians. That demonstrates a great deal of wisdom on his part.