One of the stronger (in terms of product offering) competitors to google were shopping comparison sites. They dominated the search results. Then google pushed a

One of the stronger (in terms of product offering) competitors to google were shopping comparison sites. They dominated the search results. Then google pushed an update that pushed them down. However, the manual reviewers really liked them, so in the end, comparison sites resurfaced. Then google changed the manuals, which the reviewers used, so they had no option but to downgrade shopping comparison sites. So, how is this not malicious altering of normal search results, so you can push out competition? How about insurance? How about travel? How about google+ imposed on youtube? How about changing ToS of android for OEMs?