The 7 or so people who switched did not seem to affect Canon's bottom line. Joking of course, but for as much as folks talk here, the broader Canon user base is not switching systems every iteration/product cycle based on what the competition is doing.
I suspect that the feedback from the sports/fast action crowd was that 50mp was too much. I beleive Nikon went 45mp because they felt they really needed to do something statement wise. They have little of the market, and weren't in a place with their mirrorless mount to go after agency contracts. So they did something that the smaller and only slightly more mobile enthusiast market would really latch on to. All just my own speculation of course. One thing Canon is really good at is knowing what the pros - who account for the vast majority of their revenue - want. So if this is 30mp, its not because Canon couldn't do more, its because they know this is what the intended market wants. There were plenty of reports on the R3 from back in the day by pro users that corroborate this. The forums, which love MP above almost all else, could not accept it.
See my comment above. And for the record, Canon has had a 50mp sensor for quite a while. See 5DS/R. They have the ability. They know the market.
Brian