Coder or update damaged my site?

My coder created site using my PSD files, so after few months of troubles and argues we managed working site. At the end, he told me “its not possible to make” on almost everything i wanted…anyway:

– i paid him money
– changes all paswords / mysql, ftp, and deleveled his admin profile to user prodile
– we needed some extra work to be done, so we hired new coder
– he got the money
– site is still working good
– now i deleted all the testing profiles including first coder′s profile
– site is suddenly working like 40% – no profiles, all the posts moved to concepts, homepage dissapeared etc..
– so i talked to new coder – he fixed it up in a few hours
– he told me “previous coder had to damaged this”.
– but previous coder wasnt able to reach mysql, ftp or his admin profile..

I have 3 conspiracy theories:

– an WP update could damaged site ( firts coder wasnt the top coder..)
– old coder put some kind of javascript which reacted on deleting his profile
– new coder destroyed site on purpose to get paid for fix (whats strange, he knows this old coder, and have negative experience with him too..)

Where can be true?

Please let me know what you think is possible.