>>212510340L functionally lived his life as L, so that trick would work on him
>>212510644Everyone figured it was a singular entity conducting all the killings from the fact that all of those criminals were dying specifically of heart attacks, in waves which corresponded to times when Light sat down and wrote, all over the country and in circumstances like them being in their jail cells.
If you listen to L in the broadcast trap, he's still in cope and denial that it actually is magic bullshit happening and appears to have been holding out hope that it was some kind of conspiracy, a hope dashed when his rando bait guy dies within a few minutes live on TV.
Batman has the advantage of knowing magic is real.