It was never brought forward for standardization and quickly got replaced by protocols that were. While it used UDP or TCP 443 it was a custom protocol so clients had to implement it manually and you couldn't run an HTTPS server on the same port (without modifying the HTTPS server/load balancer). It also relied on a separate certificate infrastructure.

Shortly after DoT and DoH came along as standardized proposals with fewer NIH issues and more interoperability. DoH also has the bonus of looking like standard HTTPS traffic to the resolver. Technically e.g. Google could host DoH on google.com/dns-query and it would be hidden in the deluge of HTTPS that already goes to google.com.