Look no further than VMWare torching their userbase and salting the earth. Short term gains over long term longevity. Riot is not special here- they are being shortsighted.

Hmm, good point. I'd argue that VMWare's user base was more solvent (is that a right adjective? English is not my native language), but i don't think this argument would be in my favor.

You sub to services which are monetarily motivated to stay ahead of a business which gains little from fighting on this front more than ‘good enough.’

And subscription costs too raise the bar to start cheating. Not everyone would pay to have upper hand in F2P game. Those who are willing to do it can be hand-picked by reports and manual review. We don't know their "definition of done" in fighting cheaters - maybe decreasing number of cheaters by 80% is an acceptable result? Maybe those 20% of remaining cheaters can be accounted for as "really good players" - those exist too. That would solve the problem.

This wasn’t a dire situation. As long as league (or any online game) has existed there have been anti cheat mechanisms in place.

We both don't know that, if we are being honest. If it wasn't problem at all they probable wouldn't have done anything at all - or they'd do something far cheaper. This is a speculation - i can be wrong about state of things.

Also,

Short term gains over long term longevity.

I think there is a shitty pattern — if everyone is making same bad decision (good short term, bad long term), it makes this decision not as bad as it would be otherwise. If you are the only one who is forcing players to install possibly-malicious software, you look really bad. But if every (or majority) of competitive multiplayer games requires it, this idea just doesn't sound that bad. If you already have malware on your PC - what changes if you install another one?