Without a safety net, a financial crisis will quickly move a middle class citizen into the ranks of the poor.
Without an effective public school system, citizens can't intelligently cast a ballot, and become vulnerable to propaganda and misinformation.
A regressive tax system ensures that there is plenty of government money to support the activities the rich need, like defense and infrastrusture, while suppressing upward mobility.
Suppressing citizen participation makes it easier to manipulate government.
Why destroy the middle class?
It's not anything personal, they just use up too many resources. The middle class want a life that is very much more expensive in terms of resources than the life of a poor person.