Why are there many protestantn denominations and all them say they are christians but Jesus founded one church?

and they are many churches.. I don't think Jesus founded many denominations.. then why? if the men made denominations then they are wrong because Jesus didn't say to his church to divide in many pieces.. I have seen eastern orthodox and roman catholics can trace their history to the first church but not the protestantism except to martin luther.. who made the lutheran church and after that many denominations claimed to be the true.. christian chuchers or protestants