If this were actually true, I'd guess one of:
(1) The probes, like ours, are not designed to return and have a limited life span. Maybe they just gather and transmit data until their power source runs out or something on them breaks and they crash.
(2) Maybe there are thousands of probes or even more (even from multiple sources!) and only a small percentage of them crash. Of course one would assume we'd be seeing them more often if this were true.
(3) We shot them down. That's not impossible, especially if they are just probes and were not designed to deal with something intelligent intentionally flinging high velocity chunks of metal at them.
The last could easily occur if we mistook them for e.g. Soviet/Russian or Chinese surveillance craft and they repeatedly refused to respond to orders to withdraw.
Why would someone send probes here? This planet has been broadcasting "possible biosphere right here!" for at least hundreds of millions of years to anyone capable of doing spectroscopy on the light it reflects. You wouldn't be able to see detail from another star but you could determine things like atmospheric makeup and conclude that there is very likely to be something interesting here. You'd see a ton of oxygen (which is hard to explain abiotically), water vapor, traces of hydrocarbons, and possibly evidence of sunlight being captured by something complex (photosynthesis) vs just reflecting off rocks or ice. Lastly the planet has a large moon and is not tide locked to its star, both characteristics that increase the odds of something complex evolving here (as far as we know).