By having his mother appear to St. Juan Diego, God showed how much he loved the indigenous people of the Americas. Even today, the Mexican people have a special mission to evangelize the Western Hemisphere.
The Immaculate Conception may have been formally declared in 1854, but it had been developing in Catholic doctrine for centuries.
God creates great saints and small saints. Does this mean he does not love us equally? Yes.
Mary knew how to respond to big events happening around her.