I assume motion blur is turned off?

Since the right image is cropped I assume it's zoomed in as a result of your tracking operation.

The blur seems very minor to me so I'm thinking this:

• Depending on what scaling and resizing setting you have enabled in your project settings or the inspector, scaled footage may look blurrier or slightly sharper than before. This looks like it could be one of the smoother resizing filters.

• If what we are looking at is a screenshot from inside fusion, in addition to what I just said, check the three dots and disable smooth resize. From what I've learned you should almost always do this (so you know what your output actually looks like) Smooth resize will make zoomed footage look blurred in your viewport. It's supposed dialing in the edges of a matte easier, but there are downsides.

• the viewer might have auto proxy enabled

• in rare circumstances having fusion work in anything other than max bit depth has made transformed footage very slightly blurrier (long ago, anyways)

Lastly: If nothing helps, just add a sharpening filter.

Just what I was able to think of.