I think these are the two key points of that whole sorry affair.
1. The Lib Dems thought the Tories would play nicer with them if they were in coalition together - completely overlooking the point the Tories don't even play nice among themselves (cf what's going on with Brexit at the moment and the party within a party that is the ERG seemingly intent on bringing down a Government of their own party).
2. Putting aside the various and extensive criticisms of the Tories the one thing they do very well is politics - and that's how they managed to spin things the way they did, to the detriment of the Lib Dems. People used to moan about New Labour spin doctors like Alastair Campbell and Peter Mandelson but they're mere amateurs compared to the Tory machine when it gets in its stride.