I'd find it hard to believe that the airline cooked up this scheme just to avoid paying for hotel room at Tenerife. The most likely explanation is what was conveyed by the airline. Forget about a "standard flight time" - it's irrelevant to your question at hand. The estimated flight time is calculated specifically for each flight with the latest forecast route, atmospheric conditions, etc - and that is what would be used for the crew and dispatch to judge whether they will depart within the time rules. But actual experience during the flight often doesn't precisely match what was planned and forecast - atmospheric conditions, actual routes and altitudes, etc. And that can lead to issues such as what you experienced. It's by no means proof of some sort of subterfuge (and you'd have no way to prove it even if it were, short of a lawsuit and subpoenas of airline records or something crazy drastic like that!).

Besides, I'd be willing to bet that for every passenger who shared your feelings that the airline should have bumped the flight to the next day and put everyone in a hotel, there is another passenger who was glad to just be home even if it was very late, rather than having a much longer delay (possibly until quite a bit later the following day).

I've been through similar types of disruptions, often with poor communication from the airline, when I'm tired and grumpy and have had enough (and a couple of times with my wife, and in years past, also with our kid - which is even less fun in these situations). It sucks no matter what, so your frustration is understandable. Though once some time has passed it becomes a story to share and even laugh about. Anyone who flies enough will have similar tales. But in any case, it seems the most likely explanation is the one stated by the airline. On the bright side, they were proactive with compensation and pleasant in interacting with the passengers.