Electrons do not turn into black holes because they have a very small mass and are governed by the laws of quantum mechanics, which prevent them from collapsing into a singularity.
No, electrons cannot become black holes because their mass is too low to overcome the forces of quantum mechanics that keep them stable.
The relationship between electron mass and black hole formation is that an object must have a mass greater than the Chandrasekhar limit (1.4 times the mass of the sun) in order to collapse into a black hole. Electrons have a mass that is much smaller than this limit, so they cannot form black holes.
No, there are no known conditions under which electrons can turn into black holes. Even under extreme conditions such as in the core of a neutron star, electrons do not have enough mass to form a black hole.
Black holes form when a massive star dies and its core collapses under its own gravity. This creates a singularity, which is a point of infinite density and gravity, and is surrounded by an event horizon, the point of no return. Electrons, being too small to form a black hole, play no role in this process.