Then why did the practice only catch on and spread like wild-fire after crime had already begun its plunge?
And why, after crime has continued to drop dramatically, has SWAT-ification continued to increase (if not accelerated) rather than plateau or even drop in response?
When EPA and Department of Agriculture have their own SWAT teams, you know that SWAT teams are more for status display between high level bureaucrats than for any real need to fight off the nefarious activities of Dr Evil.
Blaming unions would probably have worked better, back before the banking crisis forced many communities to do exactly what you suggest can't be done.
That said, you do raise a good point that it's career-suicide to advocate reducing police budgets in the US unless absolutely necessary -- and even then it isn't ever well-received.
(Which makes the (in)ability to actually reduce staffing a secondary problem, at best.)
But none of that excuses continued growth in the face of plunging crime, let alone the acceleration in use of such tactics.
And why, after crime has continued to drop dramatically, has SWAT-ification continued to increase (if not accelerated) rather than plateau or even drop in response?