The cooler wasn't seated properly or too much paste can be a problem.
That happens some times and is hard to detect on install. Just a little crooked or off center or not quite tight enough on the screws.
I did it before. Cooler moved while putting screws in and I didn't realize it.
Glad your running lower temps.
They should drop as the paste sets over the next day or so.
Keep an eye on it.