What are some reasons for hypersomnia, other than sleep apnea and messed up circadian rhythm?

2 stand out: Hypersomnolence can be a reaction to many prescription and over-the-counter medications (including the ones you've listed) as well as some supplements. Depression is a common cause. Hyoscyamine/imodium are drugs used together to treat irritable bowel syndrome (often associated with depression ; anxiety disorders). Other medical conditions can cause this too so get it checked out.

Narcolepsy: There are many reasons - insufficient sleep syndrome, narcolepsy, idiopathic hypersomnia are a few examples. Medications can cause this as well. Restless leg syndrome, poor sleep environment, frequent sleep interruptions can also contribute to hypersomnolence. Sleep is important to our health and well-being, phycially and mentally. If you have symptoms, consider a sleep evaluation.

Many reasons: there are many reasons. Hypersomnia is essentially is excessive sleepiness. This could be caused by poor sleep hygiene, narcolepsy, and many conditions that could affect how well we sleep so you can have hypersomnia secondary to restless legs syndrome or chronic pain.