Because he felt he was under investigation for collusion. Now he has been cleared of the charge of collusion by the Mueller Report,
so recently he said he would hypothetically accept information (or collusion) from a foreign country to bring down a political opponent.
He should realize, however, that (hypothetically) any country looking to do something like this, is
interfering in our political process,and that country has a specific goal in mind when it interferes, like division in the US. So...