The value rises because it is a superior store of value and has international transaction ability. Chinese investors highly value its international transaction ability since they can't freely exchange USD with CNY.

Although many shops accept bitcoin payment, as long as you can exchange it for fiat money, you will always get a fiat loan to spend and wait for the bitcoin price to appreciate many folds and repay the loan with a tiny fraction of your original coins, this is a no-brainer (see my signature why bitcoin will appreciate forever)

And, any ponzi scheme or bubble theory does not apply to money itself, a perfect example is fiat money, although it has no intrinsic value, everyone are still joining this ponzi scheme day by day