The taste of Semana Santa that we experienced in last June's Corpus Christi celebration is what I'm remembering, and I'm multiplying it by, oh, a hundred at least. The religious floats are much larger, the crowds much denser, the people more serious and pious than they were last summer (and they were seriously pious then).
It's the holiest week of the year for Catholics, and in Sevilla, that's abundantly clear.