As I understand it, Del Monte made a few mistakes.

The first was related to COVID. Sales of canned goods spiked during COVID. They misinterpreted this as a permanent change and invested accordingly.

Second, they did not find a way to compete with store brands, which are no longer at a quality deficit vs. more expensive name brands like Del Monte.

Finally, they didn't address changes in diet that (as I see it) makes sugary syrupy tree candy not something people want to eat. Carbs are recognized now as seriously unhealthy. Ozempic and related drugs may have also affected this.