You'd have to read the article to get at the context Musk referred to.
Here's it is:
When Trump used the word "bloodbath," he was discussing China's reported plans to build cars in Mexico and sell them cheaply in the United States."We're going to put a 100% tariff on every single car that comes across the line and you're not going to be able to sell those cars if – I get elected," Trump said at the Ohio rally Saturday. "Now if I don't get elected it's going to be a bloodbath for the whole, that's going to be the least of it, it's going to be a bloodbath for the country. That'll be the least of it. But they're not going to sell those cars."
Is Trump speaking in tongues and Musk providing the interpretation? Did he mean people would take to the streets if China builds cars in Mexico? Autoworkers would no longer exist? The economy would crash?