I know he's old- but this decline seems crazy? I know the team is abandoned can that have anything to do with it? Noticed while scouring free agents - he's playing a lot, no injuries... What am I missing?

https://www.whatifsports.com/HBD/Pages/Popups/PlayerRatings.aspx?pid=4278215

We can only see his current ratings via the link.

Current season is plenty to see he's going down in a hurry. The main thing is that he's old. Low temper/patience might have something to do with it; not sure how they play into development but logically they'd have some effect. The high makeup has probably slowed his decline by a season or two, but at 37 that's not enough. We also don't know yet how the development changes will impact growth/decline.

You can't just look at stats in a vacuum.  Bad seasons sometimes inexplicably happen without any change in ratings.

He missed most of the previous season due to injury.  That probably contributed a lot to his decline.  But without being able to see previous ratings, it's impossible to see exactly what his decline has been, or if the amount or rate of decline is "crazy".

Do coaches ratings effect player decline as well?

Yes.

I only see his current season also. Just never seen someone decline so much during a seasons where they are playing and healthy

While it's largely true that pitchers will hold their ratings longer than position players, into their late 30s, I've found that when old pitchers hit the wall - and it happens at different ages - they go down hard, and yes I've seen it happen in-season.