the article in your link is quite comprehensive.Bit like Brexit, it seems to stem from Cameron getting cosy with Huawei and interwining roles for mates with Huawei UK
December - David Cameron defends Huawei investment
Following American senators once again insisting that Huawei equipment posed a security risk, David Cameron defended the earlier UK-Huawei £1.3 billion deal. He said that Britain had a "proper system in the UK for examining whether investments in the UK are pro-competitive and whether they're in the national interest".
Huawei controversies timeline: Everything you need to know
A list of controversies involving Chinese telecoms giants Huawei, which has faced growing accusations of links to the Chinese government and potentially using 5G for spyingwww.computerworlduk.com
Huawei gives access to source code to their customers, enabling them to add their own security layer, a far cry from the practice of their competitors. To me, that's enlightened policy, a bit like open source software.
It seems to me that the USA feels threatened by Huawei. Maybe the real reason is if we buy Huawei kits, we can stop the Americans spying on us at the same time we stop the Chinese.