There might be more to see behind the curtains than we think regarding the strange case of Randy and the Aliens. A project that started such a long time ago has of course had its ups and downs and probably seen the end of the tunnel of possibilities more than one time. Obviously the game has been built, rebuilt and then taken apart again several times.
Good marketing kills bad products!
Now, the real mystery is of course why they kept on showing a version of the game so different from what would later come out. As a marketing guy I must say I am very surprised by the discrepancy between final product and the marketing material. It is such a fundamental thing not oversell a product, at least to that degree. All differences between the promises made about a product and what the product can deliver is very damaging both in the short and the long run.
The difference between what was promised and what was delivered I call an expectation gap. All expectation gaps will turn into emotional reactions. When the gap is negative you will get disappointed and feel cheated. When the gap is positive you will get positive reactions and people will spread a positive word. (side note on spreading the word. Rule of thumb says that a disappointed buyer tells 3 times as many persons about a bad product than a satisfied customer tells about a good product).
So, the simple fact is that if you make a very good marketing campaign for a bad product it will in the long run actually make it sell less. The marketing will bring a critical mass of disappointed customers to complain to their friends and warn them about the product. There are several cases through history when products sold better in markets in which they had no marketing than in markets where the marketing effort was high. The other way around, to undersell a product, will of course result in fewer people wanting to buy the product. (In the case of games it probably might help the reviews since reviewers will get positively surprised).
This might not have been a mistake!
This is, as I said earlier, very well researched and its about the first thing you learn in marketing 101. So why did SEGA do this huge mistake? My answer is that they probably didn't. My guess is that after the game was delayed for so long, SEGA decided to make it a launch game for the new generation of consoles. This would explain the very good looking game we saw in the preview material sinced it was aimed for more powerful consoles. Current console generations simply couldn't handle all the graphical goodies and the AI resource hogging and when they changed course and decided to launch it now due to some unexplained reason (perhaps IP rights or economics or something like that) all the changes needed to strip down the game broke it. I can easily see a game break horribly when you take it apart to make it fit into a weaker system.
I choose to believe this is probably why this calamity went down. Alternative reasons all boils down to pure stupidity and in this day and age businesses and marketeers should, and must, know better.