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I've noticed that some maples will bloom after their leaves emerge and some oaks will bloom before their leaves emerge.

I know that many plants time their blooming so as to be the only thing blooming at that time - to reduce competition for natural pollinators.

I doubt that leaf emergent is dependent upon pollination because there may be reasons why pollination would not occur - ie heavy rain.

Trees store food reserves for the next year and make the buds prior to fall - that is how they can make flowers before leaves emerge.

One big mystery to me is how trees know it will be a wet summer and thus we end up with a Mast Year - when there are just massive quantities of nuts in most of the trees? That decision to go all out on nut making has to be made in the previous year and then that spring...

Maybe they always produce an overabundance of buds, and then the decision is made later whether to put resources into growing them?

The sugar maples, for example, store nutrients in their roots for the winter, when the tree doesn't need much food, since it is "hibernating", then when the weather gets warmer the root sugar flows upwards into the tree limbs to nourish the leaf buds until they get large enough to perform photosynthesis. (This flowing sugar is what is harvested for maple sugar). A similar process occurs in most trees, the difference being the amount of nutrients stored, and whether they go to growing leaves to start the photosynthesis process or to growing flowers to get pollinated to allow the tree to reproduce that way.

(If you look up maple sugar farms on the web, there are some that give a great description of the whole process and how it works.)

To add to the above... consider how the seeds are distributed. A maple tree creates single or double 'helicopter' seeds, depending on species of maple. The wind catches the seed and they spiral away from the parent tree a short distance. This creates an ever widening stand of maples. Fruit trees, like apples, spread their seeds by the animals that eat the fruit and deposit the seed in a little mound of fertilizer a distance away from the parent tree. In nature, you'll find stands of maples, but fruit trees are scattered.
Trees that rely on bees for pollination have larger blossoms. Trees that rely on wind for pollination produce a high volume of pollen.
Most trees set more fruit/seed than what will develop. Weather conditions will prune the excess. Man will prune fruit trees to leave fewer fruits, but ensuring larger fruits.
I never thought much about the timing of leaf and flower development, but cold weather fruit trees will leaf just as the flower petals begin to fall. Most of the other large flowering trees in our zone will do the same.