I am using Pro. I have tried Mosaic to New Raster, Mosaic, and I have tried importing two rasters into a raster data set and a mosaic data set.
I cannot seem to "lose" the extent of the one of the images. When merged or mosaiced it consistently blocks out the extent as no values or does not port over the overlap.
What am I doing wrong?
What it looks like when I import or try to make it:

What I would like after (image shows with symbology with mask on):
