There was a substantial overlap between the then Internet Activities Board and the committees associated with ISO/IEC 7498, and it was far from dominated by telecomms companies at the time. Indeed, Lyman Chapin of BBN was in ca. 1992 the chair of both! Other overlappers included Christian Huitema and IIRC Dave Katz.

The OSI reference model itself originated with Charles Bachman (Honeywell, then IBM).

So far, no telecomms companies to be seen.

Telecomms companies and agencies were more interested in EDI in the form of X.400(84) and to some extent X.500 directory services, rather than in the lower layers, and while they were heavily invested in X.25, they were not the biggest pushers for the connection-oriented lower layers -- there were plenty of private X.25 networks operated by government agencies (including many non-PTT ones; bear in mind that the CCITT of the time was national governments represented by their local postal-telegraph-and-telecommunications ministries; the U.S. and Canada were huge outliers in having privately owned commercial telcos). There were also research & education networks with X.25 underneath, including CSNET (largely based in the USA) which was definitely part of the TCP/IP-speaking Internet.

OSI's problems weren't in the people involved or in the (admittedly heavy) formalisms that go into ISO/IEC/CCITT/ITU standards, but rather that the idea was to redo TCP/IP "right", and that included supporting difficult to reconcile goals, like supporting both connection-less and connection-oriented protocols in most of the lowest of the 7 layers, and then mechanisms to provide interoperability between CO-only and CL-only talkers.

At the time, well before FPGAs and ASICs were accelerating routers, and when megabytes of RAM were expensive (and slow), OSI appeared too heavyweight compared to TCP/IP, and that is one of many reasons TCP/IP won. OSI reference implementations were expensive rather than free as in beer (sort-of); compiling up your OSI elements took considerably longer; an OSI-equipped kernel was fat (too fat if it was only really talking ES-IS and nothing else); and so forth. SMTP/TCP/IP was what members of the OSI subcommittees were using to communicate with one another, in spite of the existence of EAN for X.400 and some native OSI CLNP (AlterNet, UUNET's internetwork, in the very early 1990s carried real CLNP traffic between RAND and several other organizations).

Internet protocols did benefit from the OSI development work; good ideas from IDRP found their way into BGP4; IS-IS is still the IGP of choice for some large IP networks; LDAP, SNMP and others absorbed good ideas from X.500 and EFTAM; and of course DSL and OTN systems have a lot of OSI in their DNA.

Finally, the U.S. government's GOSIP and similar programmes for mandatory adoption of OSI networking elsewhere probably doomed OSI networking much more than politics (and personality conflicts) among people involved in actually making the standards in the various bodies, both international (and national) and in the IETF and its close relatives. Taking profile "short cuts" to roll out OSI networking rapidly in that way raised the real possibility of fully conforming OSI networks (and stacks) that would nevertheless be mutually incompatible!

Unfortunately many of the lessons learned in the failure of OSI networking were not applied in the process of choosing and standardizing a successor protocol for IP, and here we are a couple decades later with IPv6 being a compromise specification designed for speed of roll out... (In fact some of the wrong lessons learned in the very early 1990s of OSI networking are in IPv6 today: the expectation that being CPU constrained, routers must deal with relatively short, fixed-length, fixed-format fields (rather than, say, something self-describing) is front-and-centre in IPv6 addressing and headers generally. Concerns about overheads are also well-reflected in IPv6, and for terrestrial applications, those concerns were obsoleted by the turn of the century.)

"A hetereogeneous world is an advantage". Well, try explaining that on the IETF mailing list as a reason to support concurrent development of a successor protocol to IPv6.