Hard to tell from pictures unless you have seen this exactly as it is. What do the cracked pieces feel like? Hard? Soft? Brittle? If delaminating fibreglass, I would expect to see glass fibres and I’m not seeing that. Is the cracked material under or level with or over the keel bolt washers? If under, I would think it was part of the bilge structure (original). If under the washers, then you might be looking at removing bolts and washers, cleaning out the bilge to solid material, building the thickness and strength back up to design specifications.
If the material is at level with top of or over the washers, then I would think it occurred after the factory build. Could be a previous owner applied this to ensure the bilge was waterproof and safe from water intrusion and delamination. Or it could just be a spill or leak of something that has been in the bilge a long time. The size of the cracks in the material suggest to me some kind of contraction as if the material has dried out or reacted badly - like a material or substance not designed for outdoor heat, cold, contraction, expansion or maybe a bad epoxy mix and pour. If it can be determined that this material is not part of the original bilge structure or added to solve a real problem with the original bilge, that the keel bolts are tight and secure, then I would just clean the stuff out and get back to sailing.