The market-driven principles of the domain trade mean that a domain is only worth as much as the buyer is willing to pay. It is for this reason that criteria such as market potential and usability play such central roles in determining prices. Values can change immediatly and without any warning. The price of a domain that was once of little interest to anyone in years past can skyrocket once, for example, a newly founded company takes interest in that same name.
To find popular phrases I opened up the Google Keyword Planner. This free tool by Google, allows you to find out how often a word or phrase is searched in Google. A phrase like “Yoga Mat’ has on average, about 10K – 100k monthly searches. That’s A LOT. However a more niche phrase like “Good Yoga Mats” only has 100 – 1K monthly searches. These seem similar, but I wanted to focus on the exact popular phrase that people are searching for.
At the end of the day, the owner of this domain name let it expire and didn’t renew it. So while there may be many legit reasons as to why they might’ve done that, one of the not-very-legit reasons could be that the domain is “dead” in some way or another. In other words, it’s no longer useful for the original owner because of a penalty or otherwise. If so, it's unlikely it'll be of any use for you as well.
There’s an important distinction to make here between domain flipping and website flipping. The latter mainly refers to buying and selling full websites. By full websites, I mean websites that actually have content and more often than not have traffic and revenue. When buying and selling websites, the domain name matters less as the main value there is the content, traffic, revenue, history/reputation, sustainability and growth opportunities. The same can’t be said for domain names where you’re just selling “the name” and hence it’s all that really matters.