Yes, I do think they bought DTV with the intention to shift it over from DBS to OTT delivery but it was still a stupid move given what they paid combined with the fact that cable TV was already in long-term, likely irreversible, decline. If they wanted to offer a nationwide OTT cable TV service, it would have made much more sense financially NOT to buy DTV with its fleet of satellites, etc. and instead just transitioned their existing Uverse TV service from managed IPTV to OTT. Or perhaps they could have bought PlayStation Vue from Sony, rebranded and tweaked it, and encouraged their existing Uverse TV customer base to shift over to it during a 6-month phase-out. (I'm still wondering at what point we'll see them begin phasing out Uverse TV and trying to shift those customers over to DTV Stream.)
Whether it was a good idea for AT&T to buy Warner Bros. and launch the Netflix-style HBO Max service, eh, that didn't work out either. But it was a better long-term bet than doubling down on the fading cable/satellite TV business. And there was really zero connection between the two. If they wanted to get into the content and direct-to-consumer streaming game with HBO Max, there was no need at all to have first purchased DTV.