Only May contract has gone negative, June's still above $20. That could go lower too if vehicular traffic doesn't pick up in May but I initially assumed the negative prices have become the new normal.

It hasn't, just oil can't be stored for long and all storage is full right now https://twitter.com/drdanchoi/status/1252305885256450049

Once people start moving and storage gets freed up the price will shoot right back up.

This thread on HN is a great overview of what's going on with negative oil: https://news.ycombinator.com/item?id=22929316