Not an astrophysicist but I'll take a shot:

Because the inverse square law governs the reduction in light intensity at a certain point from another radiating point source, the amount of photons that will reach Hubble from a star as far away as this one is very, very small. There would be large periods where intervening cosmic dust and clouds would obscure/absorb photons enough that no photons made it to Hubble, and hence we wouldn't see that distant star at all. Even as bright as a supernova is (10 billion solar luminosities) some stars are so far away that the inverse square law and intervening dust and gravitational fields still rob nearly all photons from reaching Hubble. To us, it appears as though nothing's there.

Enter Einstein's revelation about gravity: when the photon streams from the distant star pass by a gravity well at a certain angle, that distortion of spacetime can focus the light into a focal range that points at us and we can see the star we wouldn't have been able to see for its faintness... because like a camera lens grabbing light and focusing it into a small area, the gravity well is bending photon paths to converge into our path.

The "special help from the cosmos" is there actually being a large gravity well (like a galaxy) that's perfectly in the photon path between that distant stars and Earth, providing us with a gravitational lens to see those photons which would otherwise not have reached us, or at least have only sporadically reached us at single-photons-at-a-time intervals.

Related: read Kip Thorne's The Science of Interstellar, it deals with gravitational lensing and a lot, lot more :-)