For some people pooping immediately after eating can be normal.
The reason that some people poop immediately after eating is due to a natural gastrocolic reflex.
When you eat the foods and the foods go into your stomach your body releases natural hormones and those hormones tell your colon to contract to help move food through your colon and out of your body.
Some people have more of these hormones that get released and sometimes faster than other peoples and it's normal.
However some people may have more digestive issues than other people which could be a health issue that causes a person to poop immediately after eating.
So if the issue of pooping immediately after eating just suddenly started then you may have a health issue and need to see a doctor.
However if the pooping immediately has been happening all your life then it's likely just a normal thing for you.