So is this an admission by the US government that they were expecting other countries to a) deny their markets to Huawei, and then b) turn to the US (primarily Cisco and Juniper) to supply their equipment.
They've suddenly discovered that there are actually other network manufacturers that are neither Chinese or American, and have suddenly realised that they might not be raking in the millions after all. (Because let's not forget that the real reason for going after Huawei is to stifle the competition for US products)
I'm not sure that this is as clear as you suggest, but in truth I doubt that Trump sees anything but a bargaining chip in his trade dispute with China. Given his lickspittle attitude to Putin and carelessness with security generally—oh heck, Trump probably doesn't even know how to spell Huawei. He probably couldn't find distinguish Taiwan from Japan on a line map of the world. He actually manages to make our Prime Minister look knowledgeable about the world. Cretin.
But IMHO he has done the right thing, albeit for the wrong reasons. I am an unapologetic China sceptic, and in any case, as I've said before: it's capabilities, not intentions that matter here.
I have no idea who persuaded the idiot Johnson that there is some unbridgeable gulf between the "periphery" of a network and its "core", or who then went on to claim that UK security could magically protect against malicious actors routing traffic hither and yon—because that is what they're doing, after all. I wonder which part of the word "n∙e∙t∙w∙o∙r∙k" Boris failed to comprehend? But I do believe that allowing a Chinese-controlled company to place soft- and hardware inside our networks is absolutely insane. Some of the money wasted on the Brexit fiasco would have been great for building a home-grown, British system, come to that. The providers may be hyping 5G but there's no real urgency, when you come down to it. For most people it will make little difference to their lives, except higher phone bills.
But there. I think we can already see a steady trend towards the new government producing reliably bad, dumb decisions and brain-dead policy. Huawei. HS2. Heathrow. Red lines. Counter-terrorism.
It ain't gonna be pretty.