Honestly, I don't think this is a new phenomenon per sé. Politicians being quick to take full credit for good news isn't groundbreaking (and the masses quick to blame politics for what may be beyond anyone's control is an interesting parallel)
What's changed is how brazen, barren, and hollow Trump and MAGA have exposed the GOP to be. Under his guidance they've collectively had the finesse of a third grader and this radically exposed how little they're contributing in terms of policy.
As an example, look at Affordable Care Act. Trump claims to replace it with something better, but after years they've produced almost nothing to point to as a substitute, and it's glaringly obvious to anyone slightly interested.
By contrast, if you roll back to the debates on gay marriage, Republicans threw a 'separate but equal' token civil union around, which had enough meat on the bone to fuel a discussion.