The ATP rule was implemented to get pilots more exposure to aviation before stepping into the cockpit of a 121 airline. The Captain of the Colgan accident was a 200 hour wonder, then slung gear at the pay to play airline Gulfstream. He had several training failures and lacked basic airmanship skills. He had more than 1500 hours when he killed all those people in Buffalo but had he accomplished a standard stall recovery when he got the stall warning and pusher, this wouldn't even be a discussion. If he had instructed to 1500 hours or flew boxes in IFR solo or any number of low time jobs, he would have been better equipped to handle the thing you're supposed to perfect as a commercial pilot. Since regional airlines couldn't be trusted to weed out bad pilots, the government mandated the pilots they hired have more experience.

Don't be naive. The 1000/1500 hour rule going away wouldn't solve this crisis. Lowering it to 250 would only shorten the timeline of getting to a regional by 1-2 years. The only thing it did was show the cracks sooner.