Great minds...
Ron Dittemore stated that this insulation foam was waterproof. I don't know if that's accurate or not. I do tend to doubt water traveled from the surface to the interior booster wall. I don't think it's absolutely impossible that enough penetration occurred to create weakness, and thus a peel off.
I would suspect that water penetration or absorption was a very high priority in design specifications. If this insulation were to become waterlogged, the additional weight to the boosters would be massive. Cracking and separation would be very critical, as we can see.
The water issue is a bit iffy for me either direction. This may have been a factor. It may not have been. I'd suspect rain fell on other missions on the pad. It should be quite insightful to do a detailed study of several of the missions that experienced a significant amount of rain on the pad, and how that affected the insulation before and after launch. Preferably, those missions would involve low temperature conditions.