Just an assumption, but SM had it easy with Girls Generation and TVXQ, so they were going by brand to bring them popularity. They debuted Exo and they shot up to the top as well. But the 3rd gen taught them that the name SM was not enough to become the most popular group. As proven with the mid level of Exo and RV, so now they're trying everything and anything for Aespa and NCT.
What the... stop this history rewrite. EXO didn't shoot up to the top at all. In fact, for a year and a half they were called a 'flop' and mocked by stans of other companies and competing boy groups, due to their lacklustre results and weak debut. Only when they had a megahit with Growl, things started to take off.
But that should tell you everything, that the 'SM brand' with the megasuccess and mega popularity of SM groups like SNSD, TVXQ, Super Junior couldn't get EXO the flying start that YG and JYP groups with less effort could at their debut.
In fact, all SM groups consistently have weak starts, only to rise up in the years ahead.
I also find it laughably wrong how EXO are called 'mid level' when they were the #1 boy group for quite some years since 2012 and #2 boy group when BTS became #1. If that's the definition of 'mid level' you might as well call TWICE mid level for having BP above them.