What I don't understand is that Twitter makes it so difficult for new humans to sign up for an account, how are the robots getting around it?

I wanted to create a second Twitter account, but almost immediately after signing up it was blocked for "suspicious activity". I hadn't even posted yet. The only way to resolve it was to add a phone number to the account, but I only have one and it was already assigned to my first Twitter account.

So I was stuck.

How on earth do the spam robots do it? There are so many.