I am not a computer, so I am not sure why, but a few good advantages of the bishop taking is you take control of the d-file, giving you access to his back rank and other pieces. It also keeps his rook on the 8th rank, as if he moves forward, you have the possibility of Rd8#. Hope this helped 
why is Rad1 not a blunder
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Rad1 is in fact a bad move, but its just not enough worse than your other also bad options to meet the computer's threshhold for a blunder. As Deirdre says your getting smoked regardless. Computer probably termed rad1 a "mistake," or an "inaccuracy" which are the terms for errors that the computer scores as less serious than a blunder, but the free analysis on this site is so bad that I dunno, maybe it really did term it a good move which would be lol.
Because it is RAD!
DeirdreSkye wrote:
Rad1 is a very good move because it helps you lose an already losing position faster and play something else.
lol i won that game in the end (bullet i think) XD
I think because it gives you some center control, sure it's a sacrifice, but it's a way of containing the situation. There's not many good moves so what's next: control the center, an open file, and get rid of a dangerous bishop on g4, to do this you sacrifice an inactive rook -- 2point loss. It's the best the analysis machine can do for you.
Oct 6, 2018
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#7
Its ok because it breaks the bishops pair which is almost equal a queen, and also gives you control on the d1 file which threatens back rank checkmate if red moves its rook out of the back rank. It also allows you to threaten the bishop on c5 by moving your bishop to e3. What ever the case red being short that bishop would make it easier for him to blunder a few moves later, and being bullet I bet thats what happed. I think red in this case would do better not to take the trade.
magnusshields wrote:
Its ok because it breaks the bishops pair which is almost equal a queen, and also gives you control on the d1 file. It also allows you to threaten the bishop on c5 by moving your bishop to e3. What ever the case red being short that bishop would make it easier for him to blunder a few moves later, and being bullet I bet thats what happed. I think red in this case would do better not to take the trade.
thanks for that and knight to f5 would have been better as it misplaces the white bishop
in this postion i played Rad1 and the bishop took my rook so why isnt that a blunder. when i analyze the game it was a good move