"Some of the major manufacturers have had very specific security doors in them for years."
Yes - it's called lawful intercept. If you want to provide carrier-grade equipment, you need to support the ability to direct specific traffic to law enforcement systems for further analysis.
You can even find out how to configure Huawei equipment to do it with a simple google search (i.e. https://webcache.googleusercontent.com/search?q=cache:be6czF9UBSAJ:https://support.huawei.com/enterprise/en/doc/EDOC0100504796%3Fsection%3Dj00b+&cd=3&hl=en&ct=clnk&gl=uk&client=firefox-b-d).
Why is Huawei under attack now? Primarily because they have a significant technology lead on western communications equipment providers. Huawei have undercut competitors historically in competitive tender processes (thats a statement rather than a judgement) and western companies have relied on their intellectual property to prop up their revenues as the Enterprise market has disappeared - a number of miss-steps across the industry (Marconi's demise, Nortel's bankruptcy, Nokia's mobile division being uncompetitive in smartphones resulting in their carrier business suffering from underinvestment, the Lucent-Alcatel merger providing limited synergies/value, and further merger challenges within Ericsson-Lucent and Siemens-Nokia. While Cisco/Juniper/others provide routers/switches for the IP portion of the systems, this is generally a tiny proportion of a telecoms providers estate by value/functionality).
The attacks on Huawei are around the levels of comfort western governments have with a Chinese communications equipment provider, but the arguments presented are largely "what if" at present - I'm not convinced there is solid evidence that they may cause issues if the market remains diverse and alternatives remain.
Financially, I'm not sure serious alternatives to Huawei/ZTE will remain in 5-10 years if Huawei competes purely on features and price as the alternatives will struggle to survive, or at least become minority players in a Huawei world. That's more a judgement on the western telecommunications companies rather than an attack on Huawei, although Huawei have certainly benefited from China's industrial strength.
For the NordVPN issue, it will be interesting to see what appears. I would guess it was development/testing code to assist with operational issues around availability/failover/fault detection, but I'm surprised they didn't register the domains for themselves to avoid issues with others doing it and grabbing the traffic.