I don’t know if Ilya contributed anything technically to OpenAI in the recent 2-3 years. He is broadly thanked along with Sam in GPT4 List of contributors, he is not mentioned in ChatGPT list of contributors, he is again thanked for advice in the GPT-3 list of contributors. The folks who resigned upon Sams ouster, Jacub Pachocki is credited as lead of GPT-4 , Greg Brockmann is credited for multiple things in GPT-4 ( he was the lead for training infra setup).

All of them would have left if Sam left, if anything letting Sam go would significantly hamstring OpenAI than letting Ilya go.