It’s not about speed, but energy. Virtually all satellites are gravitationally bound to Earth. Think of Earth’s gravitational potential as a funnel. The satellites sit somewhere on the walls of the funnel. Now, next to the Earth’s funnel, there’s. much deeper funnel: The Sun’s gravitational potential. But between where the satellites are and the point where the Sun’s potential starts attracting them is still a big “hill” or wall separating the two funnels from each other (the top of that hill is the Lagrange Point L1). So to get a satellite out of Earth’s potential to a point from where it could “fall” towards the Sun still requires a large amount of energy.
It’s not about speed, but energy. Virtually all satellites are gravitationally bound to Earth. Think of Earth’s gravitational potential as a funnel. The satellites sit somewhere on the walls of the funnel. Now, next to the Earth’s funnel, there’s. much deeper funnel: The Sun’s gravitational potential. But between where the satellites are and the point where the Sun’s potential starts attracting them is still a big “hill” or wall separating the two funnels from each other (the top of that hill is the Lagrange Point L1). So to get a satellite out of Earth’s potential to a point from where it could “fall” towards the Sun still requires a large amount of energy.