If they suspect stolen items they can suspend the account and require proof of purchase or extra ID verification (to make it as inconvenient and/or risky for a criminal) instead of just banning it forever with no explanation.
Probably not with the scale of frauds they receive. The fastest method is to auto-ban and analyze. Ebay did the right thing here, unfortunately, its popular amongst carders.
ID could be faked or stolen credit cards can be used. In fact, dropshipping(ordering items on the fly, automatically, from a backend webstore - e.g. Amazon, Aliexpress, taobao) on stolen credit cards, or even pretending to do that without shipping part, is so prevalent there's a DEF CON talk[1] on that topic.