Note, I worked in that SCIF for HPSCI and handled cybersecurity issues while there.
Because Members of Congress (and their electronic devices) are high-value targets for compromise by foreign intelligence services.
Failure to follow this protocol can violate the security of the entire SCIF.
I cannot emphasize enough how serious this is.
If they don't want to give them up, they should have checked them before entering.
To disrupt testimony from a DOD official on how the President endangered national security for both the US and Ukraine by withholding military aid, the President's allies further endangered national security by storming the SCIF with their electronic devices.