I don't think that chart shows what it seems like it shows. There were plenty of pre-2018 outages that don't show up there: https://hn.algolia.com/?dateEnd=1545696000&dateRange=custom&...
An alternate interpretation of that chart is "After the microsoft acquisition, they got serious about actually tracking outages."
That said, anecdotally, it's felt much worse over the last 6 months. I'd guess it's a combination of MS-induced quality drops and AI-induced scale increases.