Yes, some techs are overhyped (chatbots, finance stuff) but deeplearning has delivered a lot of incredible working applications. It is not just hot air or marketing hype.
Expert systems were not just hot air or marketing hype. Usefulness of a subset of new AI technology is irrelevant. A winter or contraction is caused by expectations not being met, and it seems, at least to me, that investors/funders have already started expecting superhuman performance in image/speech recognition, and there's a lot of expectation even in robotics, which will probably not be met by actual results any time soon.