Some possibilities:
- a new popular project added Bokeh as a dependency
- an old project with Bokeh as a dependency suddenly became more popular
- some notebooks on Binder that use Bokeh suddenly became popular
- a MOOC that requires using Bokeh just went live
- a large company with centralized environment management added Bokeh to their setup
- dev velocity on a project that includes Bokeh jumped, increasing CI use
- PyPI made some change in their reporting methods
And many others I am sure I can’t think of of the top of my head.
Download numbers can be impacted in many ways, so they have to be taken with a fairly large grain of salt. I definitely don’t pay them as much attention as I used to, except when they need to go into a grant proposal, etc.