Along these lines, one of my sites has ranked really well on Google in a very crowded space for a long time. It got there by 5 year old SEO techniques. But it has always had great user metrics, eg bounce rate, time on site etc.
There really is no basis in such a crowded space for it also to rank at the top in Bing. I kind of viewed this site as an "I got lucky google loves it out of 10 million results". But Bing continues to show it equal love over the past few years, and I'm convinced that it ranks well on Bing simply due to the traffic and metrics from users who find it through google.
Could be wrong, but Bing results match Google results far too much for pure coincidence from two totally separate algos. If I were Bing or another search engine that wanted to emulate Google, I'd rely heavily on user data.