[Azselendor]

Because network execs want money. The dumber a show is, the more likely more people will watch it. Thus the more people that watch it means the more advertisers will pay to advertise in those time slots for that show. Shows like Invasion have limited audiences and thus advertisers avoid it because the auddience will reach a specific size and sit there. That means after a while, the audience ignores your ad and won't buy stuff.

That's when the advertisers pull the ad and the network execs don't get money. Then they take their rage out on the show in question and it gets cancelled.

But they aren't stupid, they are money grubbing sons .... you get the idea with no responsibility.