Investment has become a fast guaranteed returns at all costs kind of thing. That means that while it would cost nine years to build a nuclear reactor and twenty five to break even, the reactor could operate for a century because they're required to maintain it due to how dangerous it is. Meanwhile a gas plant can be built in two, break even in five, and operates for twenty years before falling apart from neglect because a gas explosion doesn't create nuclear fallout. This is also why coal fired plants are still running despite external pressures to render them extinct; the owners know the ROI and like the short term projections.