One of my known's website was doing well and then suddenly it was away from the SERP's. Even it was not visible with the name of the site and only 1 contact us page was visible. I guess it was penalized and something wrong happened. As a suggestion, Google ads started and to everyone's surprise, the homepage and other sitelinks emerged. Question is- is it just the Google ads or due to other reasons as we tried to take away videos from homepage and making other changes.