Why mysql multiple column index match from left?
it simple and very clear for understanding without technical details:

1,4,1
1,5,1
2,1,4
2,3,1
3,0,2


1st column is sorted

2nd column sorted independent for each cluster in 1st column

3rd column sorted for each 1+2 cluster

so, (2,1,x) will always after (1,4,x), but it is not true for (x,4,1) vs (x,1,4)