That's just the Overton window shifting. As the window shifts more too the right it appears to the wing-nuts that the left is moving away from them.
Look man, really the left just wants higher education available for all, equality for all (we've had to fight tooth and nail just to allow same-sex marriage as an example), healthcare available for all, and to still have a planet we can all live on in 30 years.
You guys are constantly getting in the way because you'd rather gargle corporate balls and shovel money toward the rich hoping for a trickle-down. You guys stand for nothing but opposition, it's in your DNA. Seriously, what does the right actually stand for that benefits all? When was the last time the right was on the right side of real social issues? You're CONSTANTLY in the god damned way. Always fighting against women's rights, civil rights, gay rights, etc.
The right is tribal AS FUCK. For example, when Obama was president 22% of republicans supported bombing Syria for using chemical weapons against civilians. Fast-forward just a few years later and now 86% suddenly support the same exact thing now that Trump is in office. A fucking wild 64 point shift. For context, democrat support was 33% under BO, 32% under Trump. They are consistent because they won't completely shift their beliefs for the party like republicans do. (source)
Give me examples of where the left has gone off the deep end. Not some fringe bullshit, what are examples of the left as a whole pushing further left?