User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-2602:306:CD9A:C860:1999:D3D0:B3E7:CF47-20190219114510/@comment-34061653-20190222220139

It's true that Rias doesn't rely on Crom too much. Crom didn't participate in most of the matches in the preliminaries and despite that Rias and her team was on a winning streak. The game in vol. 23 was the first game Crom participated in and he only did it to show off in response to Issei's performance of nuking the field. Rias team could've beaten that Ultimate class devil team without Crom. Again, vol. 23 was the first game participated in and this was at the end of the preliminaries since her match against Vali was the last one before the main stage and even with Crom on the team, Rias still lost. Basically Rias made it past the preliminaries without Crom. Meanwhile Issei needed Ravel's intellect in every match in the preliminaries. That's the difference.

Also you're looking at it the wrong way. Issei does well in forming tactics in 1 on 1 fights but as for strategic battle plans for his entire team, he falls short and he relies on Ravel for that because she's the tactician of the team. Ravel gives out the intructions and tell people where and what to do depending the situation. Despite Issei being the King, he follows Ravel's intructions. In volume 9 Issei only showed promise that he could potentially lead but that's it. Rias has much more experience because she's been doing it much longer. Again volume 22 is proof of this given Issei's inexperience at leading. Here's the quote:

Under ordinary rules, Hyoudou Issei-shi[1] relies on sheer power to suppress his opponents with light blasts, but under the special rules, his actions are actually unfavourable. It is evident that Hyoudou Issei-shi, who has attained various honours in actual combat does not actually have a very good understanding of the Rating Game as it is an entirely different thing.”

The critic sighed, and then continued onwards.

“After all, he was formerly a player who was a symbol of strength for the Rias Gremory team that tends to rely on power to win. When put in the position of commander like this, it’s no wonder that he is unfamiliar with the rules and is unable to adapt. Not to mention that the same power-type contestant Xenovia—”

As shown Issei doesn't know how to lead and it makes his team look sloppy. Meanwhile we go to Rias team.

"The display finally showed Rias’ team. Rias had also obtained several straight wins. Compared to us, she had won much more gracefully, and had also received a highly positive evaluation. Coupled with Rias’ natural popularity, the media was presenting her in a favourable manner."

Do you now see the difference?