They sourced funds, not from reckless foreign speculators (there were such, but they did not buy low-yielding Irish bank bonds! ), but in a highly liquid international market for what were considered safe bank bonds and deposits.
Instead, the destructive competition was for market share in loans to property developers, and to those who would buy what the property developers and construction firms would build. Unless they sold out before the crash, shareholders of the banks lost out because of this seemingly reckless competition, as did the holders of subordinated bank debt.