One-character .com domain names can be considered the most sought-after digital assets on the internet, but why is that?
Many companies, even from the inception of the internet, have realized that by using memorable and iconic brand names, people find it easier to remember and locate them. Just like easy-to-remember phone numbers, simplicity often yields better results.
English words are often used to shape the brands of international companies and seem to resonate with a global audience. Domain names with the .com extension (now synonymous with the internet) are the most popular choice. A single-word .com (e.g., Apple.com) is unique and cannot be replicated. There's only one in existence. Therefore, certain positive and memorable words in the .com extension are highly valuable.
Iconic and memorable .com domain names can address many potential issues, such as brand name confusion due to the spelling or length of the domain, email-related problems, and overall brand credibility. When you hear a domain like Ring.com instead of Ring.biz, there's a sense of integrity, sounding like something anyone could own.
Many of the all-time best-selling domain names are in the format of a single word followed by .com. Examples include:

Start-ups upgrading to these premium single-word .com domain names after achieving success are also quite common. In the early stages, most start-ups often opt for cheaper alternatives like .io domains, but once they become well-known, the benefits of upgrading to a perfect .com become apparent. Examples of established brands include:
SumoMe.com >> Sumo.com ($1.5 million)
MyMint.com >> Mint.com (Undisclosed)
PacificPillows.com >> Pillows.com (Undisclosed)
HelloExtend.com >> Extend.com (Mid-six figures USD)
Qihoo360.com >> 360.com ($17 million)
RestorationHardware.com >> RH.com (Seven figures USD)

The trend of single-word .com domains remains very active, as reflected in recent sales below. It's worth noting that reported sales figures are just the tip of the iceberg. The majority of significant domain sales go unreported, so these examples only scratch the surface of the real market.
Carrot.com - $565,000 - September 29, 2019
Links.com - $797,361 - June 25, 2019
Nursing.com - $950,000 - June 9, 2019
Voice.com - $30,000,000 - May 30, 2019
California.com - $3,000,000 - January 20, 2019
Zoom.com - $2,000,000 - December 14, 2018
Kush.com - $500,000 - November 15, 2018
Files.com - $750,000 - September 12, 2018
Christian.com - $600,000 - August 10, 2018
Snoring.com - $502,225 - July 16, 2018
Sleeping.com - $502,225 - July 16, 2018
Inception.com - $550,000 - July 8, 2018
[Source: NameBio.com]