He won by 150,000 votes, and Michigan has ~240,000 Muslims that can legally vote. A lot of them probably won't vote, just like how most people won't vote in general, but according to polls 83% percent of them voted for Biden (64% nationally, interestingly, but it was different groups doing the polling). If he lost the Muslim vote, he would have to have every other demographic stay at the same level of support as 2020 to pull a win, but support for Biden is pretty low in general.