they started as musically. was launched by two dudes, popped off by then got purchased for 1 bil by bytedance which already owned a more unknown version of musically, tiktok.
they merged the accounts so people on musically (which got popular due to the death of vine, rip), wouldn’t have to make a new account, then grew to what is now the last version of tiktok. memes and different trends with specific user made sounds was what made it what it is. they didn’t have to fund creators, people wanted to join in on the dances and trends. challenges would also rise in popularity, which had celebrities join in and do the popular challenges for free pr (brings in their audience)
after the death of vine, there was a huge void left for a short form video client that you could scroll on forever and ever on. so that was probably the biggest jumpstart for them. also covid.