By ruffing a club you would be able to establish the long clubs if the suit divided 4-2. On the second club West discards the 10, confirming the expected 5-1 break. You next lead the K to draw the one outstanding trump, discarding a club from dummy, and East throws the 6. It is good strategy to put pressure on the opponents. Even if you can't see a definite conclusion, the more opportunities you give them to discard, the greater the chance of an error.
Average players miss many opportunities where a trick can be gained by leading all the trumps.
It's like the trump suit is some kind of a security blanket for them. On this trick West discards the 8. This contract is too delicate to be throwing away tricks. We're getting down to the nitty-gritty. It appears that East has shortened himself in diamonds, and it is critical to lead that suit.