Why riskier? They have more of a moat don't they? The large capitalization needed suggests they will face less competition. It's more difficult for competitors to gather the necessary capital to compete against them?
What I've written here was the conventional wisdom for most of 200 years. Much of the Industrial Revolution played out when merely concentrating together capital was seen as an engine of growth. Rockefeller did not need to sell innovative gasoline, he only needed to use cash flow to buy up monopoly positions, one small region at a time, until he had the cash flow to buy up monopoly positions nationwide. Economies-of-scale meant that merely concentrating together capital was a path to greater profitability.
The last 25 years were an aberration, during which time big companies could be built with small initial investments. But over the course of centuries, the opposite was more common.