That happens when you post rubbish videos. Tiktok gives everyone "test runs" that's why sometimes you see videos with no views or likes on your fyp. If people don't like, comment or they instantly scroll away from your videos, tiktok won't feature you anymore to new people. No one wants to see their fyp full of nonsense low quality content.
You need to post videos that are high quality and interesting. The first two seconds of your videos are very important. Good audio, video quality, editing, subtitles/captions... You have to get to the point instantly to draw attention. There are no shortcuts or tricks to get viral.
Keywords can help to target people who have watched similar videos in the past. If people like your videos, interact with them and subscribe, then those people will see your videos in the future too. More likes/comments/shares= more views. It is very simple.
It's all about you and your effort. It's impossible to get famous on Tiktok if your content is not good.