Where it's hosted has nothing to do with it. Doing a lift and shift with a creaky e-Commerce platform isn't going to make it perform better. You really need to use the native services.
This site shouldn't have gone down though, they should be using better software.
Do you think they care? They could have spent thousands on better software / hosting but to what end?
They still sold every card they had and can't even fulfill all the orders they've taken. I'd imagine they had only a couple of hundred cards if that.