All I could say is that if there were a clear way for monetizing their user base musical.ly would not have been sold for that price. But it is not very relevant to Bytedance's valuation or main businesses either way.
musical.ly never had the same level of success TikTok now has, and it probably hasn’t focused on monetization at the time it was sold. Plus Bytedance owns quite a few apps many of which are extremely popular