Why are my file sizes so large for extremely short videos

I am editing clips for my TikTok... and so I have cut a small clip from one of my streams and edited it. Nothing overly fancy tbh. I exported it, and it took a little longer than usual, but whatever. I go to upload it to TikTok and I'm told it's larger than the 2GB file size limit. And I'm all "NANI?!" So I go and check the video size... IT'S 4.64GB. 

This is a 1:40:08 mp4 file. There is a freeze frame, a fade to white, and text wipe for special effects.  The animated YT mp4 I have in there to advertise my channel is 88 kb. I have two audio files, both mp3s: first one is 12Kb, the second is .98 Mb. 

So I go to re-export the video and check the settings. Literally the same settings for the video I edited right before it, which came out to 21.3 MB. The estimated file size is 28GB. So now I'm just confused. 

What is going on?????