What are the underlying factors driving their popularity? How do memecoins differ from traditional cryptocurrencies?
really it just comes down to a speculation at the end of the day, back then at the age of ICO before meme coins are this popular people are speculating on altcoins, though speculation on altcoins still pretty much going on till these days but there are people that prefer meme coin because they are trying to find a hidden game that starts from zero and reached hundreds millions of market cap, people snipe because they want to have a share of cake of that meme coin that could become big in the future.
just imagine buying with $500 already allows you to own few percentage of total supply of meme coin at its early phase, if the meme coin got somehow valued with market cap of $50m and beyond, you already making good money, but since meme coin landscapes right now are deploying thousand of meme coins a day through platform like pumpdotfun then the chance of getting such hidden gem probably 1/10000 and it's getting worse each day.

the recent update of pumpdotfun which is the biggest meme platform in solana will just make things worse as I've said earlier, so many people will create meme coin just to get that 0.5 SOL, i'm pretty sure it will destroy the entire meme coin ecosystem.
- Wasn't there a hacking issue at PumpDotFun? That's where the platform was abused, as far as I know. Although it's really cheap, less than 2 dollars can create your own meme coins immediately on that platform. So many meme coins are released every hour or every day; thousands of meme coins are created like that.
That's why, in this era, we have to be careful when choosing the meme coins that we invest in; most of them are just hype and rugpull most of the time.