There are many possibilites, Like Rich people confused to spend his money, Marketing strategies (To make an hype on his platform since most of sold nft with ridiculous was sold outside opensea) or some money laundering scheme.
NFT concept was powerful for sure but on today market it's just another some short hype while there are tons of potential.

Well, mostly people here didn't take any meme coin seriously since it didn't have any real use case but i don't say it was bad too, As you said doge it's already on the market very long and it's also become alternative coin to sending from exchange to exchange since the was really low but for now i think most of meme coins it just some pump & dump scheme.

I think Solana and Ethereum it's, Solana with up to 50k TPS And ethereum with upcoming 2.0 Update, Both of them it's my favorite right now for long term and for short term you can see some good NFT-Based Project like Wemix, Rangers Protocol, Knight war also take a look to upcoming Iluvium Blockchain-based games, Beside some hype there are some good coin with real use case that grow slowly but steady like Arweave and AIOZ.

Basically most of them created for some pump & dump, You can see tons of new project with ridiculous total supply with, With that floor price it more easier to pump but it's not really good for long or short term investment, If you can just never fall to some coin that have fish pump & dump scheme.