This was when a lot of people were saying Beal could be the next Ray Allen (LOL) and Harden just finished (what the general idea was) a choke job in the Finals. Beal's stock was way way way higher than what it should have been. Harden's stock was at a pretty low. Wizards, probably (like most middling franchises do) outsmarted themselves, and missed out on getting a real max player for a SG who probably wouldn't be anything better than what Harden was at that time.
Injury prone, probably the worst perimeter defender in the NBA. He put together one season with (barely)above average league PER(which is easier for such high usage players) in 4 seasons and he wants max? He should be happy with about 10M per year, because for sure he didn't deserve it based on his play.
The problem with the max is that it has turned into the same situation as starting QBs salaries. As long as you are a very good player who will get the same type of money that great to elite level talent gets.
Throwing the max at Beal would be a ballsy bet. Injured frequently - to the tune of averaging only 75% of games played during a year, meaning he'll likely miss 20 games If you can get past that, he's not a great defender, not an amazing passer/creator, not crazy efficient, has a pretty high usage for what he gives you (25% this year.. Harden was about 28% the first year with Dwight, but has since crept up over 30% the last two years... just for comparison sake), etc. For the Rockets it would be even crazier, since he is a clear SG, which is our only position of strength.
