On Wikipedia, regular folks like me who make changes to articles are known as “editors.” When we make these edits, they are subject to review and possible revision or deletion by other Wikipedia editors. There’s a certain give-and-take, based on Wikipedia culture and some rules, that governs these activities.
But Wikipedia has some special people known as administrators, who have great power in controlling the content of Wikipedia articles. When these people have biases, there can be problems with Wikipedia articles. This is what the article Wikipropaganda On Global Warming reports on, and it is worthwhile to read.