Why is my footage blurry when I change my sequence size?

I'm editing in a 3820x2160 sequence and it looks great. I need to make a web banner using the same footage. When I make a new squence with the web banner size of 234x60 and drag my footage in, it's blurry no matter what scale. I exported from my 4k sequence and the brought that mp4 file in to try to work around it, but have the same issue. Any ideas?