にも増して means 'more than' or 'above and beyond' a certain standard. It highlights that the degree of something surpasses a reference, which is often the norm, a past state, or expectations. For example, 普段にも増して忙しい means 'busier than usual.' The nuance is that the increase is notable and often felt by the speaker.

This pattern is fairly formal and appears in written language, news, or careful speech. In casual conversation, people might simply use より or いつもより. When using にも増して, the reference point is typically a noun like 期待 (expectation) or 以前 (before), but it can also follow a verb phrase like 思っていた (what I thought).

Note that にも増して is not used to compare two different things equally; it always implies an increase from a baseline. It often carries a sense of surprise or emphasis on the extremity.