Full of what ifs, this topic, the butterfly effect in full flow as it were. What if there was no Death on The Rock documentary from Thames, would we have had a 1990 Broadcasting Act that changed the rules and the system? Would we have had a 1991 franchise round (not necessarily in that year or maybe a year or two later) with the same outcomes under the old system?
Of course the seeds of the 1990 act were sown at the time of the Peacock Committee, two of its recommendations amongst others being "ITV franchises should be put out to competitive tender" and "Channel 4 should be able to sell its own advertising." Thatcher expected the committee to recommend scrapping the BBC licence fee. They didn't.
I've always believed the Death On The Rock documentary and the outfall leading to highest number of '0's' in the envelope blind bid ruling the 1990 ITV franchise auction to be a complete red-herring.
It was all down the Peacock Report. As he was as even his best friends described him as 'a rabid free-markerteer' that's why Thatcher asked him to write the report, which as you say, was expected to recommend the BBC being funded by advertising and the removal of the licence fee. However, his report came back with the opposite - and it was ITV that took the bullet, with the blind auction and the removal over time of the takeover/stakeholding rules.
My user name might look like Hatton Cross, but it's pronounced Throatwobbler Mangrove.