It’s hard to believe that three weeks from tonight we’ll be watching “American Idol” for the last time. It’s even more difficult to understand why the end of this once-formidable, game-changing powerhouse of a show, which even in its so-called dotage still brings in ratings coveted by executives at most networks, is feeling so rushed and anti-climactic. “Idol” ending in early April? What’s the about? Why hurry it off the schedule weeks before the all-important May sweeps period, which “Idol” handily dominated for more than a decade? (I have a theory -- see below.) Why cut two finalists a week during these last few shows -- shows that long-time, die-hard fans (and there are millions) are attempting to savor? It’s as if Fox can’t wait to get rid of it.