As @kirubakaran said it was the price and the closed source license. If search becomes a very important part of your business you better own it rather than outsource it.
Algolia is great to get started but it doesn't make sense at scale. If you have large indexes it's just too expensive.
What did the migration effort look like when moving from Algolia to ElasticSearch? Also, were you able to replicate the same user experience?
From the comment, I guess "pricing and closed source" became not OK