because the envevop of virus is made up of lipid, which is sensetive to the ordinary enviromental condition. lipid envelops are quite fragile and sensitive to denaturation (heat/cold/pH) they are more likely to be denatured and then the virus loses infectivity.

Why are enveloped viruses more susceptible to disinfectants?

Enveloped viruses are the least resistant to inactivation by disinfection, this is because the lipid envelope is easily compromised by most disinfectants and detergents. Once the lipid envelope is damaged, the integrity of the virus is compromised, thereby neutralising its infectivity.

Why are enveloped viruses sensitive?

The envelope is sensitive to lipid solvents, so that the capsid, if (easily) deprived of the envelope, may not be able to attach to or interact with the cell surface receptor(s).