Bill Zebub
“It’s probably Matt Mercer’s fault.”
Another thing you can do is integrate that background into actual information the PCs can learn and/or access otherwise. it could be as simple as Knowledge check charts: roll X, and you learn this much. Etc. But all that background is mostly wasted if the PCs never engage with it, so a good module should find a way to let the PCs learn and use that info without being infodumps.
If I am going to tie lore into the adventure without it being necessary for the adventure, then I want it to be an easter egg. E.g., the PCs learn something about the lore, and then when they find the easter egg it has some meaning (if the realize the connection). I think that moment of realization, of having put figured something out themselves, is more important than spoon feeding the players lore that I've made up.