Current setups vary by operator, but the common feature is that there is only 1 validator component.
If that component fails, then you stop validating. If that component’s slashing protection fails, you risk getting slashed. SSV is taking that one component and splitting it up - this could be into different entities, machines, cloud providers, or basically any diverse vector you can think of, and by doing so, downtime and slashing risks are greatly reduced. - Alon Muroch
There is also the benefit of easier maintenance. Nodes can be taken offline one by one to update them, which wont affect overall performance.