The market cap of its stock might but if you looked at the financial press during that episode it was full of people pointing out that there was no change in the fundamental value of the company. That’s because real businesses have things like sales volume, profit margins, property rights, etc. which aren’t entirely arbitrary and dampen the swings considerably. That’s not perfect or immune to abuse as Boeing shareholders are no doubt aware but it’s very different from something which has no grounding beyond momentary social consensus.
While I agree that there is a lot of hot air in crypto, what gives value to something like ethereum is the fact that you need it to use the network. Given people think it's useful to use that network it will give value to ether.
That does add some value but it’s fairly weak - people can always choose to switch to something cheaper, capping the maximum - and it adds its own risks: price spikes might leave you unable to perform transactions within your budget.
Yes, people can always switch. Unlike a sovereign currency nobody has a legal obligation to use any cryptocurrency, which means everyone is going to assess whether they’d be getting better value using something else.