Blurry GIF Logo

It’s because the image is being scaled to a smaller resolution than the original file, so it can fit in a smaller space. It probably looks better on mobile because your device likely has a 2x or 3x resolution screen, so it’s not actually being scaled down as much pixel-wise. (It looks fine on my 2x laptop screen, too).

The best solution would be to create the logo at the size that it will display on the website. You could scale it down with something like Photoshop that might has more options for how to scale the image that might look better. Maybe also create a 2x or 3x version for higher res screens that you can load with srcset.