Sudden death of my cat

Question
Whilst in holiday I received a call from my neighbor who was looking after my cat telling he had died.
I find it very strange as the cat was only about 4 years old (human years), he was overweight but still very active.

My neighbor has blamed me for this saying that he was overfed and that i have somehow caused his death.
I is this actually possible, my cat always seemed relatively healthy, he did on occasion have some kind of frothy/phlegm like fluid from his mouth but this wasn't a huge concern as it wasn't often that I'd see this, I was also advised that the froth was probably the cat trying to bring up hairballs

If you can is there any answer that you can give me on this as I do now feel somehow responsible or that there was something that could have been done to prevent this.

Answer
I am really sorry to hear about your cat.
It is very hard to lose a pet let alone feel guilty for it also.

It is a known fact that overweight pets as well as people are at much greater risk for obesity related diseases, including heart attacks, diabetes and liver failure.
There is no way to know what caused your cats death except by a necropsy.
Cats do drop dead from such things as Heartworm disease also, which has nothing to do with obesity but mosquitoes.
The only way to prevent that is by using Heartworm prevention.
Again, without looking inside of a cat it is hard to know what happened.
Cats don't show the normal symptoms of Heartworms so he could have had that. The first sign of them is usually sudden death- so there is nothing you can do.
There is no sense in beating yourself up over what is done. If you get another cat look into how much to feed your cat and don't over do it.
I recommend nothing but Science Diet because it helps cats live long healthy lives and keeps their weight down when fed as directed. That means using an 8 oz. cup and feeding no more than a half cup a day.
You can't do that with cheap foods but you can with SD. So if you have anymore cats I would switch them slowly to SD and help them live happy, healthy lives.
Ask your vet about heartworms in that area too. I don't know where you live but it is all over the world.
Again, I am sorry and I hope you are comforted by the fact that there was really nothing you could have done but can now move forward and help your other pets live better lives.