They had good relationships with VC funds to top up portfolio companies with extra cash (debt).

SVB would be lenient to the entire portfolio in exchange for access to the best performing companies.

i.e. Company A is a Series A start-up that needs non-dilutive financing to bridge itself to the next round. SVB would be willing to lend when no one else would. In exchange, VC’s would introduce SVB to much healthier growth stage or pre-IPO companies that need a banking partner.