A photon is not divisible, so we can't talk about wavefronts here. You can talk about two different photons travelling in parallel, but if they enter the well in parallel, they won't exit it like that, because the one close to the black hole will get bent more.
The effects are related through relativity, sure, but not directly. Light bends not because of some gravitational attraction or potential, it bends because it travels in straight lines and the straight lines are bent by the black hole. This doesn't apply to photons only, but to any massless particle. We can even take a very high energy neutrino as an approximation: It travels so quickly that when it passes past a planet or star, it travels in a pretty much straight line. But when passing a black hole, it no longer can, because the straight lines aren't straight for an outside observer.
The second effect does come into play because of potentials.
It's hard to fathom that he was able to make such stunning theories 100 years ago, with no technology to support him. Just crazy impressive.
Einstein didn't just poof his theory into existence without facts that conflicted with previous understandings:
- Speed of light was measured to be constant in all frames or reference by Michelson and Morley using a
Michelson interferometer.
- Slowdown of the decay of particles entering Earth's atmosphere, requiring technology to detect and characterize said particles.
You're conflating lack of computers with lack of technology.