Simple, I've had dealings with the civil legal system. Experience and knowledge of case law.
You would have to prove Intel was a party to the damage done, either by negligence or by willful action. Neither applies.
But that is the point I was trying to make above. Meltdown is effectively patched and solved. No longer a serious problem. Spectre affects ALL CPU's, not just AMD, Intel, etc., etc.
That is not the way it works. Meltdown and Spectre are not design defects or flaws. They are vulnerabilities that can exploit the normal functionality of the hardware in question. As such any claim against a company would need to be backed up by evidence that some form of negligence or willful act was taken by the company in question in regards to the the act of attack. That has not happened and is very unlikely as the vulnerabilities that are difficult to patch have been around for 25 years and have no known exploits. The defense attorneys will argue that because they have been around for so long and were unforeseen, they are not liable. They could argue statues of limitations, which has worked in past cases, or they could argue that they did not carry out the attack, nor could reasonably prevent it. There are mountains of arguments that could be used as a valid defense.
No company is going to offer refunds, credits, discounts or anything like that. Not the way the world works, and for good reason.
