It’s natural that sales of Sony mirrorless have been on the upward trend, they’ve kept getting better and have built a brand around mirrorless. It’s obviously they’d be outselling the competition at the moment because the camera is better and they have been building the mirrorless brand for longer.
It’s common knowledge that canikons mirrorless cameras aren’t wonderful unlikely to be outselling Sony, especially when they cost more. Quality comes into it, if Canon or Nikon were better quality than Sony then I’d have bought one of them. Too right their first attempts should be better, they’ve had years longer to do r & d.
I don’t think any of the big camera companies do an amazing job at marketing, they tend to do the bog standard same stuff over and over again.