The fact that finance is ripe for (and now rife with) technological disruption is one factor pushing the bankers in that direction, but the primary one since 2008 has been this: it's the gold rush of the decade.
A certain portion of the population, including most of the type-As, consistently pursue whatever opportunities promise the most money and prestige in the shortest time for the least work. Until the financial crisis, the best path to that end was getting rich as a trader. Now, startups offer greater risk but even faster and more tantalizing rewards. The exodus of finance towards tech will continue exactly until the next investment winter, at which point it will likely turn into a flight from SV-style tech into yet another sector - my best guess is health and bioinformatics.
A certain portion of the population, including most of the type-As, consistently pursue whatever opportunities promise the most money and prestige in the shortest time for the least work. Until the financial crisis, the best path to that end was getting rich as a trader. Now, startups offer greater risk but even faster and more tantalizing rewards. The exodus of finance towards tech will continue exactly until the next investment winter, at which point it will likely turn into a flight from SV-style tech into yet another sector - my best guess is health and bioinformatics.