I’m talking more about the UK that i know more about than other countries, i think the USA has some similarities - but all countries do have important differences.

There used to be a lot more regulation - both intra and inter nationally - that limited how much they could do in terms of international and mortgage investment. Since deregulation banks have typically shifted into investing more into the housing market and to some degree overseas (hard to observe the net position though, especially with multinational corps. and banks). Essentially I’d argue this “crowded out” domestic capital intensive industrial sectors. And generally reduced the savings multiplier in favour of more bubbly type investments - or household sector.

The conequence was that the “job” of the banking sector used to be to fund domestic (business) investment and growth - and to try not to debauch the currency too badly - at least in the post war period. They had to manage the balance between bubbles , stable investments and their non-performing loan rate, and maintain reserve requirements and central bank deposits as a buffer against bank runs .

But since 70s/deregulation they just invest more wherever they like - with less constraints in place to protect the whole system. They seem to be able to get bail outs without major consequences for management when they fuck up. (This was probaably the case in the 50s and 60s, but the other rules prevented them from fucking up too disastrously. Even back before the 30s when there was much less specific regulation there was still the “gold standard” to keep them in check to some degree.