Is the ending of DCUC due to Rainbiw Lanterns and/ Super Powers figures a factual thing, or assumptions?
For me, it is second-hand information from Mattel. For you... it is third-hand information from me that you can choose to believe or discard as you will and I won't be upset either way as I can't/won't say anything else to verify it so I understand how that comes across.
What -I- was told was that neither Rainbow Lanterns nor Super Powers were directives from DC, and were, in fact, Scott being given more authority than he'd had before over character selection. There were always figures in waves that were Scott's darlings, but apparently 15-16 were the first he had a lot of say in (the Validus and Bane waves), and 17 (Rainbow Lanterns) and 18 (Super Powers) were mostly Scott.
17 and 18 sold horribly and sales didn't really bounce back enough for waves 19 and 20 -- with the line already being cancelled internally before wave 20 wrapped production. Wave 20 was released in early 2012. MOTUC was still going and was seen as Scott's chance to prove himself - but (probably no fault of Scott, really, as MOTUC had burned through all its major and even secondary characters) MOTUC sales were declining as well throughout 2013. MOTUC was internally cancelled after the 2014/15 line-up (after it was finalized, I mean - but before it was released), which was already at the factory. Scott put in his resignation in 2014 -- because (my speculation here) there was just nowhere left in Mattel for him to run. Both of the lines he was in charge of had basically collapsed as he'd gotten more control of them, but his name was still big enough that other companies wanted to hire him.
Obviously, they quickly realized he fucking sucked at everything, since he flounced around to two of three different toy companies in as many years and then decided to stick to a YouTube channel where he literally -looks- unemployed.
Anyway... I'm confident enough in my sources to believe everything up there is fact besides the thing I labeled as my own speculation. But, as I said at the top, you are in no way obligated to just believe me.