If you can use just a bit of capital to borrow a whole lot of capital, with the only risk to you being your original capital, then you can engage in very risky ventures, getting a huge payoff if you succeed and at worst losing your original capital if you lose.

Come to think of it, that seems a bit like what SVB did. Buying long term bonds when interest rates were likely rise seems like a recipe for disaster - and in fact the logical outcome was this bankruptcy. But there was a chance that interest rates wouldn't have risen, at which point the shareholder get a big payoff, pocket it and go on to the next risky maneuver.