I admire the fact that your sticking up for Crennel because whenever a team is free falling, the coach is the first to get thrown under the bus while players and GMs get the benefit of the doubt. I agree 100% that the Browns had a lot of problems that was out of Crennel's hands, but if Crennel can't find a way to work around those problems, then why would the Browns want to keep him as a head coach? The players gave up halfway through the season, and you expect a head coach to be able to light a fire under his team. Crennel couldn't do it. I think he's a good coach, and not every coach needs to have the I-think-I-smelled-a-fart-and-I'm-pretty-pissed-about-it Bill Cowher scowl, but some teams need a coach that will stick a foot up their asses when they need it (I can think of another particular Ohio team that is in the same position). Crennel's a good coach, but obviously not the one Cleveland needs.
And there were also questionable decisions he made in games. In particular, early in the season, he called for a field goal instead of going for it on fourth down when they were too far behind with too little time left for that field goal to mean anything. He essentially threw the game away because, as he described later, he didn't want his team to be discouraged by not having a scoring drive. In short, he gave up so his team wouldn't feel bad. That's just stupid.
Also, he's struggled against division teams. He has never beaten the Steelers, and if you're consistently losing against the same team twice a year, something's not working out.
Crennel is a good coach and he hasn't been the entire problem (GM Phil Savage was first to be let go), but he wasn't working out in Cleveland. At a certain point, you have to make a judgment call and decide if this coach, good or not, is best for your team. And with his poor record, I think it's obvious that he wasn't working out.