That definitely plays a role, but I think the much bigger factor is how it lets anyone download & share the video file (at least by default, which most don't change). These days, half of reddit, twitter and discord is just filled with TikTok videos. Even Reels and Shorts are full of TikTok videos, you can tell by the watermark. So much so that Reels had to forcefully derank videos with the TikTok watermark on them.
This has helped Tiktok spread and grow very quickly. Hell the very link on this post is from Twitter and has almost 100k retweets...