People buying shares were acting on what they believed to be the true valuation. A big difference. Imagine two people are "long" on some stock. Person A decides to sell; They believe the true valuation is lower. Person B decided to buy more; They believe the true valuation is higher. One of them is wrong.

In this case, the buyers of Hertz stock were most likely wrong, although things are not yet finalized and another comment here notes that alternate plans are being proposed that would not wipe out share holders.