By spreading themselves too thin, and then through a series of events the current mono theistic gods accidentally kill themselves. (This is very sad, and I don't wish to offend anyone who was fond of them.)
So now like after a forest fire, many small gods are sprouting up.
These new gods are very similar to the Greek and Roman gods. They epitomise facets of human nature (love, war, etc), technology (farming, harvest, writing, music , pottery etc), and nature (the sea, the forests etc).
So! What would be some interesting gods to have in our modern world?
For example a modern god may be a god of fashion. He/She may help with inspiration or help a faithful new designer with a chance meeting with a fashion magazine editor etc. They could also be fickle and decide they don't like a designer anymore or go out of their way to impede a label if the owner became too prideful or something.