I think the system has become jammed with too many applications and they are reducing the invites for the time being because otherwise they wouldn't be able to handle them in time. And by applications I don't mean only EE - the visa officers also evaluate applications from other programs, such as the family program, which is where you have a huge backlog. This also explains why the typical application gets looked at by a VO, you see an update in the system, and then your application waits for weeks until another VO opens it to work on it for an hour or so, and then leaves it until another few weeks have passed, and so on.
The reduction in the number of economic immigrants planned and the refugee quota increase are just part of the reasons for the reduced invites.
As for the OINP, they obviously have a huge backlog there as well, as evidenced by the doubling of the time to AOR from 2 to 4 months. I think they took on too many applicants too fast - more than they could handle in a reasonable amount of time. So I guess they will go easy on the invites for now until they clear part of their backlog.