I’m going to defend the club on this one. Assuming we now never pay a penny to Spurs and his wages are about 5m the total outlay on him is 12.5m minus the amount Besiktas are paying for the loan. The downside of the deal was always limited and the upside if he’d recovered his form was considerable, even with the potential extra payments.
You could also argue that given the importance of it his second half game changing performance against Palace repaid a good chunk of the outlay in 45 minutes.
In fairness I'd never begrudge the club doing a deal like this, the lad was worth £100m less than 2 years earlier and we got him for free. If it worked out and he returned to form he would've been a bargain at the £40m with all the add-ons, never mind the free transfer. All in all it was probably a mix of one of our smartest deals we've done in years and also a gamble absolutely worth taking.
I think it was reported only £20m was based on appearences and the rest was based on competition or personal achievements so even if he turned out to be a decent to good player £20m would've still not been terrible for a then 25 year old England international, he's just turned out to do the absolute minimum completely, even with working with someone he claimed was an idol.
There's absolutely been cases of talented attacking young players having terrible spells under managers like Mourinho, Nuno and Conte, he had them all in a row so that was understandable, the fact he can't do a thing under Lampard or in a poor Turkish league is the signal that it's a him problem and not the environment around him.