One reason the cars race in such a big pack at Daytona (and Talladega) is the restrictor plates on the cars that minimize the airflow into the motor and drop horsepower. The result is the drivers are going flat-out the entire way around and combined with the draft can't get any separation. At that speed and with the aero packages on the cars a group of 2-3 cars or more are always faster than one car driving alone.
Last year the cars worked in 2-car groups, taking turns pushing each other. That proved unpopular with the fans so NASCAR made some changes to get the cars to pack back up again. Another change they made was to make the radiators smaller, meaning that in the past the cars could run nose to tail longer and build up more momentum. This year the motors heated up faster so you had to jump out of line more often to get air through the front grill.
Another problem last night was that the outside lines just weren't working. Guys got up there in a nice draft and just couldn't move forward like they have been able to in the past, which led to drivers less willing to jump out of line and gamble because if you jump out of line at the wrong time you just go backwards. Usually in a plate race there is a lot of jockeying around and position (not to mention lead) changes.
I am an IndyCar fan first but do enjoy NASCAR. Racing is something that you have to see in person. TV doesn't even come close to giving it justice in terms of the speed, power and noise these cars exhibit. When that pack of 42 cars wind up and come to the green flag it's really, really cool to see in person. The first lap of the Indy 500 is incredible. And like others have said, understanding the nuances of racing and the strategies make it a lot more interesting.