This is an easy answer.
If you want to write about other things, do it. It's part of the je ne sais quoi
Will the "other things" get paid well? Ask yourself, does it matter? Are you truly here to express yourself and have your readers enjoy you? If so, the hard core followers will love it. If you allow yourself to focus and concentrate on payouts, you become a content-machine for money, and to me, I unfollow people like that.. Don't be a content-machine. Use this platform to share yourself with others, and in the end, you'll get rewarded. It won't be obvious post-by-post... but the long term trend is that you will see it works out quite well.
what if I want to write about other things?
Just do it. :)