He always hated what he took to be the elitism of the Greek system. This is why he never joined a fraternity. The investigators found unruly students, decaying buildings, demoralized teachers, insensitive administrators. That is why their report has had such impact. You should include a variety of sentences in your paragraphs.
Parallel sentences are memorable means to summarizing a lengthy discussion.
As you proof your essays, you should find a variety of sentences and try to assure that you have not fallen into a pattern that your reader will find monotonous. Sequence is the order of your body paragraphs. Do not change the sequence on your reader. The pronoun that replaces a noun should agree with it in number. So should the verb that a noun subject takes.