The UK has tens of thousands of Huawei VDSL2 DSLAMs installed, I imagine most countries have similar (Portugal seems to use Huawei for nearly all of their FTTH equipment). They are not dumb pieces of kit at all in terms of computing power.

Regardless, even if it was, it is still a huge potential problem. Imagine Huawei had some backdoor code that looked for a certain pattern of data across any of the network interfaces and corrupted the firmware so it wouldn't load without being physically replaced. China then buys a load of ads and as users browse the web, they load the image with the secret string in, triggering it (one example).

Within a couple of hours enough users have seen it that the vast majority of western infrastructure is down, and needs replaced (and I would assume in this case, China wouldn't be willing to sell more!).

I think this sort of attack would likely take down most 5G anyway - as it's incredibly likely that the backhaul has some sort of Huawei fibre product in it somewhere along the line.

China et al don't care all that much about individual users.

By compromising a large network provider they have the ability to access data from enterprise and government customers. Which as we saw when the US did it is very beneficial for trade negotiations etc.

Do they though? Nearly everything these days has TLS/SSL. What would they gain from intercepting a load of encrypted data?

Even NSA said their snooping on network infrastrucure was becoming useless with the leaked info on their monitoring, which was years ago.

I really don't see the value these days of being able to intercept traffic like this. You will obviously find bits and bobs that isn't encrypted but it's not like 20 years ago where you could get everything in a few days.

That is one form of attack, but that's "the nuclear option" of infrastructure. It's a concern, but many of the concerns around 5G are persistent nation state spying activities. China is far more concerned with data aggregating and mining than it is with nuking the West. China, in general, tends to avoid cataclysmic actions that upend the current order. Especially given that most of the Western world is China's largest trading partners and a fundamental part of their economy.

China's strategic plan is spy and collect, not destroy. Traditional espionage stuff that every country does.

Then 5G is down. So what? Considering the amount of procen backdoors in Cisco devices that seems miniscule.