We've learned that data is unreliable. The highest click through rates come from nudity, or totally gross things like gore and trypophobia triggering holes. The highest CTR on text comes from well, clickbait. At this point everyone realizes this but some still don't notice that data-driven decisions optimizes for weird things.
IOT doesn't scale as well as we thought, because hardware doesn't scale at the rate of web software that we're used to. So hardware companies do more poorly than expected. Replace "hardware" with anything else that's hard to upgrade, and you get software-other hybrids like Uber and WeWork which didn't scale as well as anticipated.