First of all, Bush is a fucking war criminal who belongs in jail. And at the present the results of Bush's presidency are far, far worse than Trump's.
With that established, I think it's natural for people to look to small moments in the past when things, given the power of hindsight, seem less bleak because we know to an extent how they eventually unfolded. The Trump administration has been pretty concentrated in how much of a disaster its been so far, and while it's premature to compare it to all eight years of George W. Bush, this presidency has been extremely threatening at times. Threats of nuclear war, hints of conflict with Iran, Muslim bans, repealing DACA, attacking LGBT rights, endorsing white supremacy and it's visible resurgence during this year, and more. People aren't delusional to be worried and scared given all of that.
People don't know how bad the Trump administration is capable of becoming. The feeling was largely the same during the worst points of the Bush administration, but over the past nine months it all feels a bit accelerated. And that's draining for a lot of folks. I don't think people in here are necessarily nostalgic for the Bush presidency, but it's just a reflexive action when Trump's acting both threatening and inscrutable. Bush's mindset was at least more linear when compared to Trump's.
I know the difference between living under a fascist and a deranged fascist isn't really worth splitting hairs over, but the latter has been pretty exhausting at times.