He also spent most of his last years openly not wanting to be there but I guess there was no one else up for the job?
He was one of the very last salaried producers at the BBC - in other words, he was getting a regular, monthly wage from the licence fee, so the BBC had to find him some work to do, because he wasn't freelance and wasn't paid for limited periods.
Every year, they'd promise him he'd be moving on from Who, except no-one else would take it, so each year he was made to come back, or quit a regular income. It was a classic 'stuck-in-a-rut' syndrome, especially as JNT was sadly waiting for the BBC to commission his dream production... Which they never did. So eventually it all came to a head - ratings collapsed, JNT walked out, the BBC didn't know what to do, Philip Segal approached the BBC about making the show a US-co-
There is a persistant story that the BBC did approach someone - rumoured to be the producer of Jupiter Moon, William Smethurst - about a 1990 series, but he declined and the show went on ice.
E: *Wiki claims Paul Stone, who did Box Of Delights, was asked about taking over for Season 26. So it shows they were actively seeking someone to give it fresh legs.