Well, it's always worth to take it with a grain of salt. But considering that Embracer moved Volition from Deep Silver to Gearbox before their collapse can imply something was going on
I can give you one of them right now -
Matt McMuscles. He's a very credible youtuber who has a full series dedicated to development of games and movies. He does tons of work on researching them and tries his best to talk anonymously with multiple people who were close to development to see their takes at what happened. Other source was a someone who is well-known from Saints Row community, but I don't remember his name. Both of them had similar reports though. Anyhow, in the video I linked that first guy talks quite extensively about it
As for what was reported by them - Volition was bouncing around with continuing Saints series and then rebooting it with making a game similar to Saints 2 and Saints 3. The game was supposed to be more grounded and darker like Saints 2, but still has some silly ideas like the third game. Deep Silver's execs didn't liked this take and said to them they're more interested in doing a story about quirky group of friends that they felt could be more marketable