In my opinion the upward price action is caused by institutional investors' interest in Bitcoin. Some people who were skeptical about Bitcoin recognized it potential only after PayPal announcement.
It is really the investors.
Paypal may be one of the most popular adoption of last year but with a lot of users not wanting the services given by Paypal, I think it is the numbers of investors actually putting their money into Bitcoin. Since the fall of Bitcoin at $3K, there are a lot of people who invested hence making the price we have right now.