Who's at the source of this and what is the motive?

I've posted before about what's coming to light about senior administration people cooking intelligence reports provided by agents on the ground assessing the strength of ISIS and al-Qaeda.

The story is creepier and greater in magnitude than has been known so far:

More than 50 intelligence analysts working out of the U.S. military's Central Command have formally complained that their reports on ISIS and al Qaeda’s branch in Syria were being inappropriately altered by senior officials, The Daily Beast has learned.

The complaints spurred the Pentagon’s inspector general to open an investigation into the alleged manipulation of intelligence. The fact that so many people complained suggests there are deep-rooted, systemic problems in how the U.S. military command charged with the war against the self-proclaimed Islamic State assesses intelligence.

“The cancer was within the senior level of the intelligence command,” one defense official said.

Two senior analysts at CENTCOM signed a written complaint sent to the Defense Department inspector general in July alleging that the reports, some of which were briefed to President Obama, portrayed the terror groups as weaker than the analysts believe they are. The reports were changed by CENTCOM higher-ups to adhere to the administration’s public line that the U.S. is winning the battle against ISIS and al Nusra, al Qaeda’s branch in Syria, the analysts claim.

That complaint was supported by 50 other analysts, some of whom have complained about politicizing of intelligence reports for months. That’s according to 11 individuals who are knowledgeable about the details of the report and who spoke to The Daily Beast on condition of anonymity.

Those filing the complaint mince no words about the culture in which they had to operate:

The large number of analysts who complained to the Pentagon inspector general hasn’t been previously reported. Some of them are assigned to work at CENTCOM, the U.S. military’s command for the Middle East and Central Asia, but are officially employed by the Defense Intelligence Agency.
The complaints allege that in some cases key elements of intelligence reports were removed, resulting in a document that didn’t accurately capture the analysts’ conclusions, sources familiar with the protest said. But the complaint also goes beyond alleged altering of reports and accuses some senior leaders at CENTCOM of creating an unprofessional work environment. One person who knows the contents of the written complaint sent to the inspector general said it used the word “Stalinist” to describe the tone set by officials overseeing CENTCOM’s analysis.
Many described a climate in which analysts felt they could not give a candid assessment of the situation in Iraq and Syria. Some felt it was a product of commanders protecting their career advancement by putting the best spin on the war.
Some reports crafted by the analysts that were too negative in their assessment of the war were sent back the chain of the command or not shared up the chain, several analysts said. Still others, feeling the climate around them, self-censored so their reports affirmed already-held beliefs.

This is about people who want to murder us in our beds, and some element in our own government doesn't want us to know how far along they are in their ability to do so.

Get your brain around that.