Every sentence must contain a subject and a predicate and express a complete thought. Independent clauses contain all of these elements, which is why they can stand alone as sentences. Dependent clauses don't, which is why they can't stand alone.
A simple sentence is a sentence that consists of one independent clause. That is the case in the given example. The subject is <em>he </em>and the predicate is <em>runs after money and wants to enjoy power</em>. Since the sentence has only one subject-predicate pair, it consists of one independent clause. That makes it a simple sentence.
Compound sentences are sentences that consist of at least two independent clauses.
Complex sentences are sentences that consist of one independent clause and at least one dependent clause.