Google Sheets overrides the original data. If you want to use full names later, copy the rows, paste them to another column or sheet, and run the Split text to columns function.

This way, the full name ‘Jose Domingo Sanchez’ would be split into the first name ‘Jose’ and the last name ‘Domingo Sanchez’. Again, this would work for longer names as well.

Like Excel, Google Sheets makes it easy to split data that's been clearly defined, such as a last name and first name separated by a comma. Follow these steps to separate names in Google Sheets ...

Learn how to use the Text to Columns options to split comma seperated text in Microsoft Excel. You can do the same in Google Sheets as well.