Salesforce is the king of CRM!
Before Salesforce came into the market in 1999, Siebel was most popular CRM and Siebel target customers were enterprises and big companies, that time SaaS model was not in existent. A software was usually delivered through CDs and have to be installed on the computers. The cost of start using a CRM systems was in thousands of dollars at minimum and companies had to sign multi-year license deal to start using CRM software. Marc Benioff, then an Oracle executive, strike with an idea of making CRM software easy to deploy and affordable to acquire, it should not cost companies a fortune, he comes out with an idea of providing CRM software as a web application and charging per month per user basis and without any long term contract.
Salesforce main focus has been CRM for all these decades, now Salesforce has emerged as a platform for various softwares related to customer activities, thousands of application are listed on Salesforce appexchange. Salesforce CRM is most used CRM application in mid-enterprise and enterprise space and has almost 50% of the market share and is still fastest growing CRM company and is growing at faster rate than CRM market itself.