IL&FS default: Did rating agencies' failure to connect dots lead to crisis?

In the case of IL&FS subsidiary IETSL, for instance, rating agencies did not ask why the promoters' line of credit was not invoked despite the dues being so delayed

Did rating agencies again trip up in their assessment of IL&FS, leaving the markets with little time to adjust to the unravelling of the infrastructure company? Or do you accept the rating wisdom that at least three non-banking financial companies (NBFCs) are AAA, and more than one public-sector banks have slipped down to AA minus or even lower on their Tier-I bonds? It means these banks are more prone to default than the highest-rated NBFCs. To get a sense of what goes when a paper is rated by a credit rating, let us examine a typical one in the case