Tiktok is a very heavy energy user, both because it is video, and because it uses a lot of data to transfer that video to your iPhone. Were you using cellular data or Wi-Fi? Cellular data requires up to 10 times as much energy as Wi-Fi, depending on signal strength.
And swiping off all apps used actually increases energy consumption. Apps on the App Switcher screen are not running; they are suspended, but ready to run when you want them. If you swipe them off they are no longer ready to run; they must be reloaded from storage to RAM, which uses more energy than leaving them idle. Here is more information on this subject→Do not close "background" apps | Communities. Note that it usually does no harm (unless the app had recent data that had not been saved to storage), but offers no benefit, either.