I'm sorry to her about your dad.I suppose when people don't have much going for themselves, they clutch at things like this to feel superior.
I was reading a tweet the other day about someone who'd been sadly diagnosed with cancer and several people were in the comments either asking if the person was vaccinated, or saying things like "there's so much cancer about since the covid vaccine was rolled out". How ghoulish.
They always seem to want a simple explanation to everything, whereas there are multiple factors as to why cancer has increased - eg overwhelmed NHS not seeing people as quickly (yes it got worse during lockdown but it was bad before then too), people living longer, people exercising less and living more sedentary lifestyles, etc. Plus some of it's just down to genes. My dad was diagnosed with cancer in 2019 when it was too late to cure. But he'd lived a healthy lifestyle, he wasn't overweight, he ate well, he did all his cancer screenings and so on. He did everything right, but it still got him and his brother (my uncle), too.
It's the same story with my MIL. Never smoked a day in her life, lived in a non smoking house, etc but had aggressive lung cancer.
I can't think of anyone I know who hasn't been affected by cancer in some way whether it's a family member, a friend or even a celebrity we admire.