For Bitcoin this is about it gaining mainstream recognition, in a way it still is not recognized, since some countries want to ban it, in others it is unregulated and so on.
But for 1929 is about when even people that normally wouldn't be investing, think they are good investors because they are investing and getting impressive returns, it means the stock market is overheated, and more sensible investments are not giving enough returns.
That said we are in a 1929 situation right now, in my opinion, not only stocks keep rising, but seeing even meme cryptos skyrocketing, a rise in employment in cassinos bigger than employment in production (according to jobs data in US), and seeing people that can't pay their own expenses properly "investing", makes me think something is seriously wrong with the economy, not just in US mind you, I am seeing in other countries a rapid proliferation of investment advice online courses and coaches, rapid gains in questionable investments, a rise in popularity of scams and pyramid schemes, basically people want to save, can't figure out how to save, and are burning money in the cheapest options (meanwhile a good choice would be buy land for example, but despite me being in the top 5% richest in my country, I can't afford any, at all! I live in a "projects" style rented apartment and despite me wanting to actually farm, all my income is going in paying the ever increasing food, medicine and rent costs! I can't afford buying property, much less electronics, toys, etc... that would move the economy beyond the bare mininum).