He never saw it coming. He hadn't faced a primary challenger in 14 years. His own campaign's internal polling numbers showed him ahead by 35 points just three weeks before the primary. He didn't even bother to show up to a debate.What was amazing about AOC is she out-hustled a long-serving incumbent in her ultra-blue district.
Although, the incumbent probably took his seat for granted and didn't try to campaign hard until it was too late.
There is an unwritten rule among Democrats that they don't primary an incumbent Democrat, especially someone like Crowley who was a 10-term incumbent and the 4th highest ranking Democrat in the House. But AOC ignored that rule and to her credit she worked hard and built enough of a grass-roots following to knock him off.