The government wanted people to use Baidu (and other chinese alternatives) over Google. This follows the trend of other bans (youtube/twitter/facebook) which all have chinese alternatives.
Google was by far the most popular search engine at the time they made the decision. Other lesser search engines are mostly fine.
My guess is that it was proving too controversial to outright block Google because of it's popularity at the time, so they decided to make it appear low quality instead.
