Yes, you are.
The ISC, is a Commoins select committee, and as such one of it's prime roles - perhaps it's sole prime role is to sxrutinise the actions and performance of the intelligence, counter-espionage and security services, and the government ministries and ministers they report to.
As such, it is their role to see how well those services etc had done in dealing with acknowledged threats to Britain in those areas - in this case, ihow well they had prepared for, investigated and dealt with a clealy acknowledged threat to the integrity of British democratic processes.
It is MI5 and GCHQ (and also possibly special branch) who would actually investigate the dodgy Russians themselves. No-one else has that authority or purview.
HTH.