It's a large number of consolidation transactions, probably from an exchange and my guess it's Binance. They do them in bulk, once every 3 months (IIRC), and dump a boatload of these massive transactions into the mempool all at once, pushing up the fees, including their own. Each of those big squares is a few $1000s in fees, and they have dozens of blocks worth of transactions.

By spreading them out and maybe doing them one by one, continuously, they could keep their fees a lot lower. But no, they spend half a million USD in fees, just because they are dumb.