Hype + the market sentiment, which is bullish.
Though, as I've seen, many memes just got a bit of a correction up to 10%-15%, whereas some utility-based alts got the same, but in plus.
So it's really about the communities around these coins + the mood in general on the market.
Yes, it's basically hype, but because of the bullish market sentiment, it amplifies the hype itself. An example of a token that fits your case study is Peanut the Squirrel, it even made it to the top 100 on Coinmarketcap. Who would have thought that would happen?