The timeline of the answer suggests that this didn't happen in the review queue. Apart from that, it's pretty obvious that this is spam, so it shouldn't have been edited out, even if the answer weren't copied.
It's good that you worry about this happening to you in the review queue. While showing other answers there may sometimes help, often spammers copy answers from elsewhere on the site (or the Internet) and those cases won't be detected. Also, a First Post / Late Answer to a question with a lot of answers quickly becomes annoying to scroll through if all answers are shown. (The question itself is already shown when you're reviewing an answer.)
In cases like this, i.e. posts with a promotional link, it's good to put some of the content of the post in a search engine to check if it's plagiarized. If you're certain it's not, that would be a moment to edit out the link and leave a comment about signatures and self-promotion.
In my opinion, this should have been caught by some kind of automated review. Is there one?
Most posts like these are detected by Smoke Detector, one of the tools developed by Charcoal, a volunteer organization for combating spam across the Stack Exchange network. (Disclaimer: I'm a member.) This one was not, because the spam is rather obfuscated: even for a human it's hard to read, let alone for a computer.
