Most times it is not the altcoin we expect to move in an uptrend that particularly does that. Different altcoins move by various factors, some may come from the project owners or investors while most times come from the upward movement of Bitcoin and they follow suit. However, if you want the popular altcoins to start going high you have to wait for Bitcoin to move in the bullish direction. All the altcoins would increase because of the defect from Bitcoin. This is most case scenario and I am sure about it.
Most of the people who buy memes are people who sell some of their potential assets, but if you understand, I'm sure they won't sell their BTC just to exchange it for meme coins.
Indeed, the sensation of memes is quite exciting, sometimes if the hype is once able to provide significant profits, it is also not the case all the time. Always pump following the increase in BTC. There are quite a lot of examples when the BTC ETF before it was legalized, the price of the meme was almost up, almost on average.