Abnormal CPU and RAM usage

I've opened a simple excel file with 2000 rows max and about 100 columns. When I running a simple filter function (crtl + shift + L), the CPU usage goes from 1% to 100% and RAM from 300MB to 3GB. The system I'm using a Lenovo T14 5th Intel Core Gen Ultra 5 16GB RAM (also running on AC power with the BEST Performance preset). The file has no queries or connections. Just a simple xlookup formula for one column that pulls a result from another sheet that has 26 rows with 3 columns.

I'm puzzled why this is happening. Any pointers or remedies?