Selenium Script Execution Slow Due Too Large Class?

I have an automation project for UI and desktop app which uses java,selenium, page object model, and component object model. Few of the steps was taking more than 20 seconds time. I believe the component class was fairly large due to 100+ locators and 3K lines of code. When I split the component page further the script time was reduced to less than 10 sec. Can someone explain the technical reason behind this? How to identify the reason for slowness?