How did pollination occur without them?
Probably birds, bats and other species of insects. But there was never agriculture on today’s scale here in the absence of honey bees.
Other insects such as bumblebees did the pollination. Also a lot of the native plants were wind pollinated.
Vanilla is pollinated by the Mayan bee, a very small sting less bee that does produce honey but in such small amounts that it is not really worthwhile to keep it. Vanilla grown anywhere but in this bee's habitat has to be hand pollinated. Usually by some poor guy with a ladder and small brush.
BTW the bees talked about by O-Bummer are wild bees. There are fewer records on wild bees so he can claim their populations are declining more easily without some smart alek being able to prove him wrong.
Cultivated bees were having a rough go of it a few years back but the populations have recovered as more beekeepers dusted for mites.