Complex sentence: Perhaps the best example of a company that became very successful on the back of specialised word processing systems was Wang Computers but then collapsed when it lost its revenue from word processing systems and was not able to substitute newer forms of computing quickly enough.
Split into simpler sentences: Perhaps the best example of a company that became very successful due to specialised word processing systems was Wang Computers. Wang collapsed when it lost its revenue from word processing systems and was not able to substitute newer forms of computing quickly enough.