It's interesting that up until the 1970s, viral infections were the predominant theory for the cause of cancer (this is before my time so apologies if I'm exaggerating). This was due to discoveries like src, ras, EBV, etc, so a lot of these carcinogenic pathogens were well known and studied. It wasn't until several discoveries in the 70s and 80s that we started focusing more scientifically on genetic drivers. But it's not like these infectious drivers went away, even if they are no longer as strongly associated with the disease in the public conscious.