A dog licking people suddenly and crazily may be caused by a variety of reasons:

1. Dog licking people is an intimate behavior, which may mean that it likes and respects its owner very much.

2. The dog may want to express its needs by licking people, such as asking the owner to help get toys, Take it out to play or want to interact and play with its owner.

3. Dogs may want to please their owners by licking people, and then get some benefits, such as snack rewards, etc.