The biggest leagues are more watched by football authorities so I agree that it is difficult to fix the outcome of the match but it's not impossible. I've read of some news about probes of high ranking football officials before but those are matches in lower leagues.
I was pin pointing my post more on the big leagues, the smaller leagues In Europe and those outside Europe can be practicing match fixing and the media or public interest will let it pass under their nose.
The big leagues has eyes on it making it extra special