There are a bunch of really large transactions in the mempool, like for example this one, with 1000 inputs.
Actually, there seems to be several identical ones, for example transaction 3ab99fa9c8e7b37e560a704049552b375bb864a845c46fa053535ffd3a38fb21. Have a look at "Large transactions" in https://bitcoinexplorer.org/mempool-summary
These transactions take up 90,825vB and 363,298 wu so they would fill up blocks fast. Even though only around 5000 tx are in the mempool, 25 blocks is required to clear it.
What's up with these? Are they part of a spamming strategy?