Steam did a lot to boost again PC gaming, and besides this, PC too, like consoles, follows a cyclical trend, that's partially influenced by console trends: depending on the moments during console gens, there may be competition or synergy with PC, and in different competing phases PC can win or lose, hence the many highs and lows. Obviously 3rd party publishers prefer to have as many highs as possible for both, and this helps expand synergies.