Upvote:12
The Wahhabi ideology started as a revivalist movement (return to the roots) and quickly became strongly conservative, emphasizing intolerance not just to other religions, but to other variants of Islam. This provides a tool for dealing with the dissenters (accuse them of deviations from the party line). Also, the emphasis on the early "Rightly Guided Caliphs" justifies the (almost) absolute monarchy. Thus the ideology suites the political elite because it justifies their monopoly on power and provides the tools to keep it, so it will not be changed from above.
The people are sufficiently religious and the government is sufficiently oil-rich to prevent any attempt of a change from below (by maintaining a sufficiently high standard of living for the locals and suppressing any possible unrest among the guest workers).
Another issue to consider is that Saudi Arabia controls the Muslim holy sites, so the country have to present an "orthodox image" to the pilgrims. Wahhabism's "unpopularity with the rest of Muslims" actually helps because neither (mainstream) Sunnis nor Shiites have to fear that the other side takes over the holy sites.