Adobe wanted ECMA4 to become the new standard and to speed this process they donated the Tamarin virtual machine to Mozilla. This piece of technology is what runs at the heart of the Flash Player. With this in place, Mozilla had a lot of what was needed to support ECMA4. Other manufacturers such as Apple and Microsoft would have to write this themselves. Writing code cost money and nobody is making money from selling browsers. This and other "political" issues caused the committee to split in half.