In the topic breastfeeding; so much importance is given, then why the early Muslims had wet nurses? Why din’t they themselves fed the baby?

Before I answer the question, can you help me clarify what does "early" Muslims refer to?

Please note that the wet nurses have always been the second choice in Islam. It means if the mother, for any genuine reason, is unable to breastfeed then a wet nurse will feed the child.

Please refer to ayah 233 of Surah Baqarah

"Mothers may breastfeed their children two complete years for whoever wishes to complete the nursing [period]. Upon the father is the mothers' provision and their clothing according to what is acceptable. No person is charged with more than his capacity. No mother should be harmed through her child, and no father through his child. And upon the [father's] heir is [a duty] like that [of the father]. And if they both desire weaning through mutual consent from both of them and consultation, there is no blame upon either of them. And if you wish to have your children nursed by a substitute, there is no blame upon you as long as you give payment according to what is acceptable. And fear Allah and know that Allah is Seeing of what you do."