Why do low- and intermediate-mass stars become white dwarfs?

Low- and intermediate-mass stars become white dwarfs because they lack the sufficient mass to reach the extreme core temperatures and pressures required to fuse elements heavier than carbon and oxygen.12

As these stars exhaust their nuclear fuel, they evolve into red giants and eventually lose their outer envelopes in a process that forms planetary nebulae. What remains is a dense, hot, and compact core composed primarily of carbon and oxygen.132

Because this remnant has exhausted its nuclear energy sources and is too compact for further gravitational contraction, it is supported against its own gravity by electron degeneracy pressure. Over billions of years, the white dwarf radiates away its residual thermal energy until it eventually cools into an inert stellar remnant.3