Remove Trim/Baseboards Installed Prior to Hardwood Floors (No Leverage)
An oscillating tool is your friend. It looks like it would reach to the bottom nail. Looks like you were able to pull the top of the board out enough to get to the bottom nail. You also may be able to break it with a chisel, but nails are hard.  Get some good blades for the osc tool, I found that a cheap blade only cuts 5-10 nails.
https://www.homedepot.com/p/RIDGID-4-Amp-Corded-JobMax-Multi-Tool-with-Tool-Free-Head-R28602/206824272