We cannot know it wasn't theft. Counter-parties were sitting on the other side of the trade benefiting from the loss of value of those bonds. They earned a bunch of money, bought themselves yachts, the yacht companies stock price went up, they gave raises to their execs, who bought themselves mansions, etc, etc... This drove up the cost of living for everyone else. Now it turns out that the bank is short on depositors' funds. Instead of depositors taking the loss as punishment for doing business with this bad bank, citizens who had absolutely nothing to do with that bank will foot the bill through inflation when the government issues new currency to make the depositors whole.

It's taking money from citizens who had nothing at all to do with SVB to people who were doing business with it and may in fact have benefited from it.