I think of my pump as just another way to give me insulin. It is the same insulin as when I was using a pen and, if I eat the same and do the same amount of exercise, I need less insulin on the pump. I see no reason why the pump would be to blame for challenges when losing weight.
If you have had Type 1 diabetes for 50 year (which is a great achievement), ou may be of the age where weight loss is not as easy. The pump timing may just be a coincidence.