because uhh?
you need to reread
oda stated how much of a big deal wb getting off his stabilisers was in the sbs, and said he just didnt have space to add a dramatic scene of him coming off it, and how bad it was for his health
This is why marco literally stated wb should ordinarily be able to react to squardos sneak attack, but since his health was already rapidly declining after getting off his stabilisers, even before he joined the battlefield, his reactions and haki, in this instance obs haki was already declining.
Hence why a healthy WB can react to ace in his sleep, and MF WB couldn't even react to squardo's sneak/
WB definitely was not stronger than Hawk-Eye Mihawk at MF.