It is weird for sure, but there will always be some explanation for the phenomena experienced. It is just that we won't be finding that out precisely ! You can have a guess though, I love to think these things through as part of the hobby, often when I cannot get out for radio time. Here are a few things to consider that might make your hypothetical example come about...
It might be 35 Watts into a beam with 10-13dB of gain. (focusing that 35 Watts precisely where it needs to be. Where as your 1.5KW will be subject to the inverse square law being spread equally across your antennas omni directional pattern. (less microvolts per area of space)
Your antenna has a null at the angle required to make that contact.
The footprint of the dx coming down from the sky over the land could be at a fringe reception area where your QTH is... 40 miles up the road might be ok.
The spot in the atmospheric cloud/ionized patch may be rotating the polarization of your signal to be the opposite of the RX station meaning something to the order of a 15-20dB loss (I think). The other station not so.
And other general skip thoughts...
One station gets to destination with 4 hops and another 7 hops, due to incident angles/antenna setup.. each hop will take its toll on the signal strength attenuating it influencing what is RX'd at the other end.
Some stations you can hear very clearly but they have deaf RX or QRM on their RX end, so only a significantly stronger station will get through.
Some stations TX and RX may be influenced by more localized tropospheric effects before it hits the E or F2 layer.
I very much like to consider these and try and visualize things, fascinating.
Also I cannot quite get my head around the moment I key up that signal is radiating at the speed of light into the sky the distant horizon I am looking at and bouncing multiple times and ending up at some far flung destination within a miniscule split second... where someone just happens to be listening. Mind blowing when you think about it... makes you feel pretty damn cool, right..
The amount of times I wondered about how many hops any given contact took to be made and how wide the RF footprint was when it came down to earth... 40, 50, 200, 300, 400, 500, 600 miles footprint beaming out of the sky at some other country. Talk about an interesting hobby, that we chose !
I also like the thought of the signal doing say... 6 hops and the person who comes back to you might be at hop 1,2,3,4,5, or 6.
Radio DX is fantastic... it's as deep as your own mind allows.
