I worked at Microsoft from 2010-2012, and the crux of the issue there was that, for Microsoft users who had the Bing toolbar installed, the toolbar would track what you were visiting in your browser and use that session/journey information to try and improve the relevancy of Bing results. If a lot of people who searched for "best pancake house" (regardless of what search engine you used) end up visiting ihop.com within the same browser session, well then Bing would want to rank ihop.com higher for that search phrase.

Google noticed this, and for unique/low-traffic search terms, was able to synthetically generate enough "fake" traffic that the "fake" traffic became the dominating signal for those terms, and therefore Bing started directing users to the fake results.

The bad thing here IMO is the level of tracking of users via this toolbar, but fundamentally this seems as bad as any other digital fingerprinting or advertiser tracking as anything else that's become common on the web. This is not to excuse Microsoft for doing a bad thing, but it really had very little to do with "scraping Google", which somehow became the popular media takeaway for this.

EDIT: a decent contemporaneous article in Wired: https://www.wired.com/2011/02/bing-copies-google/, mentioning how Microsoft was using the clickstream data from the browser/toolbar, not scraping Google results per se