I'd say one of the biggest reasons for the drop off after Xanadu was just natural exhaustion. He'd been at it in a pretty constant way since the mid 60s and already had wild success and really nothing to prove. Realistically he had nothing to prove after Out of the Blue which was not only an epic creative explosion but also a huge commercial and critical success attached to a big tour. I would guess that he was probably operating on fumes during the Discovery and Xanadu period but was still really creative and productive. I think having a little 'time' before his next album obviously gave him enough mojo to create another major album with Time. But the delay of that album might have had something to do with just the general change in public tastes as well. Fairly or not, ELO was associated more with the old guard than the 'new wave' so setting the stage promotionally was probably an important consideration and likely a topic of discussion if not at Jet... then certainly at CBS. Your comparison with Brian Wilson resuming live activities is pretty on point to me. Both never were super into the idea of touring but... both recognize the love of fans and the positive energy of that type of experience. I think the problem with Zoom was that it was designed as a standard tour to promote a then current album... but it was poorly conceived and promoted and was too cookie-cutter for it to work for an artist who had been off the scene for at least a decade (and technically more from a live sense). I think both Brian, even though he kept releasing things along the way... and Jeff... could see this not as a promotional tour but as a victory lap... a love fest of fans and admirers who could come to the show not because of whatever current release or product was available but because of genuine love and respect for the artist's work. I'm thrilled for Jeff that not only is he taking the risk and opportunity to do this but that he's open enough to accept that love and respect from so many fans who only dreamed that such a tour would ever happen.