Any one can fork a coin. Then attach a significant market value to the given fork by promoting it heavily. Or if required they can do it after the fact - They can be on the buy-side and creating an ever increasing bid to pump the fork.
As for the support, you will have human greed play a big role. Everyone holding x coin gets 1 x coin + 1 fork coin with significant value which means it will create some market as well as intice miners to mine a coin with much smaller difficulty.
You can't just make random forks and have them be worth something. This is the culmination of years worth of debate and has a significant community following.
The market value of a coin isn't limited to a strict mathematical function of mining power or exchanges backing it. That's the point Matt is making.
