A core tenet of the "dark enlightenment" mind-virus that has taken hold of the valley is the idea that civilizational decline/collapse is not only inevitable but imminent, so they don't really mind getting a bigger slice of a smaller cake, as long as they are in charge[1].

However, they also are getting citizenships from other countries or buying pacific island bunkers: just in case.

1. The collapse inevitabilitism absolves them of any guilt when their actions make the world worse, since "it was going to happen anyway"

They supported it because they saw an opportunity to remove limitations on them, both domestically (see FCC, restrictions on state level AI laws, etc) as well as internationally (regulations, digital taxes, etc in the EU and Canada, for example).