Help! Visible Streaks After Applying Polyurethane Finish

I recently purchased a piece of unfinished beech wood and finished it with semi-gloss Polyurethane. After applying the second coat I noticed if you look at it in a certain light, there are many visible streaks that look like brush marks. What did I do wrong and is there anything I can do to fix this?

What I did: I began by giving the entire top and sides a light sand with 220-grit sandpaper to buff out any stains. I then wiped down the entire piece down with a rag to remove the excess dust, and then wipe it down with tack cloth to remove sanding residue. I then used a brush to apply the polyurethane to the entire top and sides of the desk and left 8-12 hours to dry. The next day I gave the entire top and sides another light sand using the 320-grit sandpaper to pop air bubbles and try to even out the finish. Wiped down again and put on a second coat. Third day I noticed visible streaks are still there.

TLDR Applied two coats of polyurethane with brush and there are visible streaks if you look at it at a certain angle and lighting. How do I fix it?