No I'm not saying the mechanism has changed, mob rule has probably been a thing since humans organised in groups larger than 5, but the scale and level of scrutiny definitely have.
I'm not familiar with the case of celebrities or Sinead O'Connor specifically, but no celebrity in my lifetime before the advent of this new wave of cancel culture has been completely cancelled the way they are today (even Michael Jackson, who had serious allegations of child molestation, had an O2 concert scheduled shortly before his death).
Even for the average person, if you lost your job due to anti-mob comments in the 50s that didn't bar you from ever finding a job again (which is the case for some today), and this is without even touching on the way some people have had their entire twitter history crawled and pulled apart from a time when they were generally very different people.
As I said, this is probably a function of social media in the modern era more than anything else.