As always, it's because they performed much better than Wall St expected, who expected another operating loss.

TSLA is particularly volatile because they run the risk (and many analysts believe) that they will run out of cash before they can achieve profitability, so their share price have carried a lot of risk that have hampered its price from its $400's highs. This surprising profit effectively significantly weakens the risk giving investors more confidence they'll continue to be around for the long term to dominate the EV market.