> Could Boeing built a self-landing reusable rocket? Almost certainly.
McDonnell Douglas is part of Boeing and (before they were part of Boeing) did the DC-X prototype.
One failure ended the program, but it was transfered from McDonnell to NASA at that point I think and funding was shifted towards the reusable VentureStar. But it did demonstrate reuse and went through a partial failure of a hydrogen explosion and recovery:
https://www.wikipedia.org/wiki/List_of_McDonnell_Douglas_DC-...
Yeah, basically exactly what I would expect - they're perfectly capable technology-wise, but they're not capable bureaucratically.
Which, if Musk has value, is where it comes in.
Could Boeing built a self-landing reusable rocket? Almost certainly. Would they have been willing to, considering it almost certainly involves failing in explosive ways multiple times? That may be a risk they aren't willing to take.