Why the drastic fluctuations in skill level from players who are about the same rating?

It's amazing how from day to day, you'll go from playing people who are playing about at their correct rating to playing a series of people who attack like a titled player. It's no big secret that chessdotcom's pairing system is rigged to create streaky win/loss experiences, but you would think they wouldn't make it so obvious.

I don't think it is "rigged" in that way. I think you've just observed that people around the same rating can play very differently from person to person or day to day. This is because chess has many factors at play (mood, sleep, nutrition, distractions, motivation etc.) which impact how a person plays. There is also natural variance which is mathematical and can't be eliminated entirely.

I'm sure they've determined that the more people they can get on losing streaks, the more people may buy their membership. But there's something up with their pairing system. Whether it's them intentionally pairing you against cheaters who they refuse to ban, or pairing you against bots. But there's no way people of the same rating can just jump this much in playing ability overnight.