DD-WRT initially gained popularity by giving users a myriad of features not typically found on consumer Linksys and Buffalo routers. With pure shell access, VPN servers, VLANs and an IPTABLES firewall, educated consumers could do some cool stuff. Additionally, businesses with engineering prowess were able to deploy these products at fractions of the prices of higher end gear.
Over time, DD-WRT seemed to upset a handful of users by having a not so open-source friendly development approach and possibly alienated many developers. It seemed DD-WRT as a corporation wanted to dictate the direction. As such, many key developers spun off to OpenWrt to create the platform they wanted. OpenWrt did not have a company behind them, but they did take a large chunk of the development community with them.
Over time, manufacturers began to add the features (VPN, Dynamic DNS, Guest Networks) originally unique to DD-WRT. Also, as chipset makers began making new chips with higher reference power outputs, the emergence of MIMO and other technical issues, it made the power boosting capabilities of DD-WRT relatively moot. DD-WRT also struggled in some cases to get good commercial driver support, and I think you've documented that manufacturer performance tended to beat out DD-WRT. Meanwhile, DD-WRT was not releasing new features, it seemed most of the development was focused on porting the solution to new hardware and trying to keep up.
OpenWrt on the other hand continued to prosper with a development community and instead of focusing on this huge bloated platform, they focused on a light weight platform with a modular package manager and open SDKs for easy development by third parties. As such, much of the corporations wishing to develop their own "cheap" solutions, tended to prefer OpenWrt. Consumers also liked the "package/app store" approach as it just makes sense. It's similar to Synology, Apple Store, Android Store, you name it... OpenWrt did struggle more with hardware support and basically only Atheros ATH9K drivers (Atheros 11n) is well supported. The WRT1900AC Open Source friendly disaster with OpenWrt sort of explains that (Marvell/Belkin/Linksys provided no support and OpenWrt head came out saying their product was pure marketing and no official relationship with any open source development).
All that said, it "seems" DDWRT NXT is a brand new DDWRT focusing on everything that was criticized about DD-WRT original. It is a new, 'unbloated' platform designed with modularity and development in mind. It appears it comes with a limited feature set of popular DDWRT features and will release new features via some package management/module approach. Very much like OpenWrt it seems.
