The question is which is more expensive for the Chinese:

Build all components locally and not be able to sell to US market. Or buy some components from US and still not be able to sell to US while being forced to agree to some US demands.

Remember, the first one also give you the option to ignore patents and licensing fees because "hey your honor we asked but they didn't want our money".

Best case for China: problem disappears in 2020, worst case: 2024. This will be a rounding error and their actions show this.

Because they have successfully subverted the Democrat politicians and were able to bribe them to look the other way while they wage a multipronged economy war on US?

Maybe. But people got a taste of a different world now, and learned that better is possible. Won't be easy to push them back into 'Can't do anything about China stealing your country piece by piece' pen now.

I don't think what happens now is only positive for US.

In the short term Huawei will loose tons of money but this could be the push China needed to commit to become world leader in chip design.