Even if he had enough personal wealth to fund the entire project - it doesn't make good business sense to do that. The Kickstarter is a good way to see what the level of interest is - and then they can budget the project accordingly. Rich people don't get rich by carelessly gambling their money away. Any big game project is a gamble. Look at what happened to Curt Schilling / 38 Studios.

And I'm sure Portalarium is a much smaller company than Obsidian.