He disliked monopolies and trusts. He was nicknamed the trust-buster for eliminating so many (cannot remember exact number sorry). He even tried to take out the SOC (Standard Oil Company) which was one of if not the biggest monopoly in America I haven't thought about this for about a week so I forgot a little I hope this answers your question
Roosevelt was named the trustbuster and the one who tried to take out the standard oil company NOT Taft.