Question

how did fungi developed​

Answer 1

because of harmful bacteria

Answer 2

The evolution of fungi has been going on since fungi diverged from other life around 1.5 billion years ago, (Wang et al., 1999) with the glomaleans branching from the "higher fungi" at ~570 million years ago, according to DNA analysis. (Schüssler et al., 2001; Tehler et al., 2000) Fungi probably colonized the land during the Cambrian, over 500 million years ago, (Taylor & Osborn, 1996) but terrestrial fossils only become uncontroversial and common during the Devonian, 400 million years ago.