I think you're both underestimating how long it takes to really get settled in and take charge of a huge corporation, as well as overestimating just how long 5 months really is.

Seems like about the right amount of time for him to start really kicking things into high gear imo.

Not for the CEO of a big company like that. 5 months is barely enough to get the lay of the land. The press may have you believe otherwise (e.g. Marissa Mayer is changing Yahoo overnight). It's a more interesting story than "she's slowly getting to know how things work while trying to fix the most obvious and visible disasters."

If I had to guess, I'd say because it took the ceo a few months to see how things are currently done and identify problems. The rest of the time I guess would be waiting for the right case to come along.

Five months may seem like a long time, but trying to fix something that's pretty broken probably requires a bit of time to understand just what the hell you're trying to fix.

"I can run a 3 man startup and change things in a week! Why can't a public traded company worth billions with thousands of employees change things in a week?"

Check your ignorance and entitlement at the door, please.