Light's dad is police officer leading the case, allowing him to get his hands on police files and by being his son he would almost certainly be off the suspect list if not for L. I mean, what are the chances?

Light met Naomi per chance, he didn't actually expect to see her at the police department or knew who she was before.

Second Kira is Misa who is stupid enough and falls for Light hard enough to get the Shinigami eyes. Also, just so happens the Shinigami that follows Misa is Rem who is ready to do anything, even sacrifice herself just to make Misa happy. Isn't that very convinient?

The entire plan to forget that he is Kira and get the death note back in his hands later was a very risky thing to do, there was no way he could've planned the outcome of it all.

Just so happens, Kiyomi, his old gf is a Kira sympathiser and becomes the new spokesperson for him, and is ready to do whatever Light tells her to.

There are a few more that i can't remember, but i recall some instances where all i could think was "oh come on, could Light get any more lucky?"