Did I cause my bunnies death?

Hi.
My bunny died a few weeks ago and I really want to know if what I did may have caused it. 3

3 days before he passed, I saw that he had dry skin and I’m not sure if I did it that day or the day after, but I decided to get lotion and Vaseline and put it on his dry spots. I put a good amount, but made sure to rub it in well and comb it out.

Then one day when I woke up I saw that he wasn’t doing well. He wasn’t eating, pooping, and he was hunched up. I gave him a bunch of belly rubs because he looked like his belly was in pain and I took him to the vet the day after I realized he wasn’t feeling well because where I live vets are closed on Sundays.

After taking him to the vet I had to take him to an emergency vet because the vets couldn’t get any blood out of his veins and then he died an hour after getting to the emergency vet and they said that they think he might have just started to have bone cancer. This is what his dry skin looked like.

Do you think it could have also been fur mites or was it just cancer. Also sorry this is so long but I really feel bad because he’s my best friend.