I didn't know 'Maine Coon' so I looked it up.. Wauw is this cat really that big?

Yes there is a difference between cats & dogs. Cats are predators, but dogs don't catch rabbits to eat, not even for survival.
Maine Coon's can become quite the chonkers. I owned me a big old 18 pound girl who passed almost a decade ago.
They are majestically furry creatures, and affectionate, loyal companion animals.
Unfortunately, they can be prone to health problems in late age, and mine began to suffer from hip dysplasia, before ultimately passing from heart related issues, around age 15.
I think 15 years is a good age for a Maine Coon, always hard to lose a loving pet. Mostly they are really a part of the family.