I've needed to do this quite a few times, but couldn't easily find a clear example online. Here's how to unmerge cells and fill values in Excel.
For the simple case where the range only contains one distinct value, it's trivial to copy the value to all cells. However, where there are many distinct values in the range, there are a couple more steps involved. This still only takes a few seconds to do.
If you want to keep just values and remove the formula, simply highlight the range again, copy, paste, and paste values only. E.g. Ctrl + C, Ctrl + V, Ctrl, V