A similar situation: The tea party folks were incredibly upset that Obama ran a big deficit. You wouldn't know it to listen to them now, but for many years the deficit was the most important thing in the political world and proof that Obama was trying to destroy the USA.
But the deficit under Obama shrunk every year, while the deficit under Bush Junior grew every year. Yet the tea party folks never made a peep of complaint when Bush grew the deficit.
So the most likely explanation is that the tea party folks never really cared about the deficit; they are just whining partisan idiots.
I'm neither a fan of Bush nor Obama, but what you've stated here is incredibly misleading (as well as factually inaccurate).
According to the non-partisan CBO data, the on-budget deficit under Bush began at $32 billion in 2001, ballooned to $568 billion in 2004, then decreased again until 2008 (the 2007 deficit was "merely" $342 billion), after which it spiked (due to the financial crisis, bail-outs, etc. with 2008 concluding with $642 billion deficit).
Under Obama, the deficit began at $1.55 TRILLION in 2009 and stayed above Bush's 2008 maximum of $642 billion in 2010, 2011, 2012, and 2013. Only in 2014 and 2015 has Obama's deficit dropped below the MAXIMUM Bush ever attained in deficit spending. Now, you might argue that inflation should be taken into account, but you'll come up with somewhat similar figures if you take percentage of GDP instead of actual deficit amount -- the first four years under Obama all were above ALL of Bush's deficits in percentage of GDP.
Or, another way to see this is that the total debt under Bush grew from $3.4 trillion at the end of 2000 to $5.8 trillion at the end of 2008, an increase of about 70%. Under Obama, the debt has grown from $5.8 trillion at the end of 2008 to $13.1 trillion by the end of 2015 (and he still has a year to go), an increase of 125% (more than doubled).
Personally, I think a lot of the Tea Party's logic makes no sense, and I think deficit spending is really essential for all sorts of reasons.
But you've also just outed yourself as a "partisan idiot" for attempting to make it look like Obama's deficits are less concerning than Bush's (to people who might care about stuff). Except by any metric the Obama deficits have been much larger, regardless of whether they are trending up or down... so to me it seems pretty logical that people who actually care about deficit spending might be concerned about the fact that it more than quadrupled between 2007 and 2009 and has stayed above 2007 levels ever since.