With no end to the tech downturn in sight, the industry’s titans are eyeing new markets. The bigger, the better: in the past year the combined revenue of Alphabet, Amazon, Apple, Microsoft and Meta reached $1.5trn, so further growth that moves the needle can only come from a giant business. One candidate is finance. What is more, that industry generates petabytes of data, the crunching of which is a core competency of tech firms. And it is…