Main reason is still because that bitcoin buyers are still confident that price will rise in due time. Lots of people shorting BTC but at the same time a lot of new investors or old investors taking on new positions = short squeeze.

Also not to mention BCH did crash, so that's doing wonders for bitcoin price at the moment.

$8000 is just a figure that will be broken sooner or later. I don't even think that $10k will be a particularly troublesome thing to break for BTC considering how fast it is rising by day to day.