SteamVR switches the active power profile when it starts, then errantly restores it to Bitsum Highest Performance when it closes.
This incompatibility can be resolved by using a 'Start with power profile' setting in Process Lasso. That will serve as a base power profile to return to when no power rules are active. You may want to set it to Balanced.
You can set this via menu item 'Options / Power / Start Process Lasso with Power Profile'.