(The railway mania wikipedia page even blames low interest rates for it! Personally I'm of the opinion that the government can set its bond coupons to whatever it likes and investors are not owed a minimum return, but there we go)

Edit: since the original comment was quite popular, I'll make some forward-looking statements: there is likewise a lot of investment which needs to be done in order to decarbonise, has major social benefits, but will not necessarily be profitable in the market. Even the highly distorted market that is energy. It may turn out that substantial negative interest rates are needed to finance the transition.