1. Expired shelf life: Check the shelf life on the cans. If the canned food has expired, the asparagus inside may rot and soften.

2. Improper transshipment: During transportation, if the canned food is violently hit or squeezed, asparagus may be damaged and become rotten and soft.

3. Improper storage conditions: If canned asparagus is exposed to high temperature or humidity for a long time, or stored in direct sunlight, asparagus may rot and soften.

4. Production quality problems: Sometimes, canned asparagus products may have quality problems themselves, leading to asparagus rot and softness.

In order to maintain the quality of canned food, it is recommended to buy fresh canned food and store it according to the preservation suggestions on the label. If the canned food you buy has become rotten and soft, you'd better not eat it to avoid food poisoning. If there is damage or packaging problem before buying canned food, it is best to choose other brands or buy fresh asparagus.