Rush told us just that over and over. Concessions and victories don't satiate them. Democrats move on to the next objective the moment their current one is reached. RINOs typically wilt before they can win just one. And they nearly always assist Democrats in realizing their goals. Democrats don't help Republicans with a vote without a huge reward baked into the bill, either.
The issue is never the issue, the issue is always The Revolution.
Suspect this follows from the core concept of Progressivism. The current state is never seen as desirable as the next state toward what is seen as "progress". To not make "progress" is seen as a gross moral deficiency and presumed to be a sign of bigotry and sinister motives. Thus stopping to carefully consider the complex reality of the current conditions of society and the full ramifications of the next step in "progress" border on heretical kind of thinking and is instinctively avoided and discouraged and "backwards". To not see the "next step" as unquestionably good is intolerable to the Leftist mind.