Gravity , as Einstein say it, is relative to the person let's say. Ok you are free floating in a vacuum and I ask you to enter a gravity elevator. You enter and the door closes as you are now standing on the floor of the elevator. Now you are told to jump as high as you can, at that moment your body goes up by force of your legs and then suddenly you are now standing on the floor. Did gravity pull you down to the floor or did the elevator move up to your feet
I inserted my own take on the elevator thought experiment.

I don't know much either, but I guess the implicit question is why does mass cause space to curve? Is there a force carrier between the mass and the space which causes curvature of space-time?

A weak force is still a force

what you're saying is not much to work on. Do you have a reference that gives more details on the link of the lack of force for gravity and particles?

I’m a bit rusty but I can get things started. In many models forces need to be mediated by particles. When no one could find a gravity particle folks started looking for other explanations. One of which involves warping space-time around masses. It allows gravity to make it look light a big object can bend light because the light follows a straight path in a curved space. No mediating particle, no speed of light delay but hard to picture.