If that is his goal, he had better make a much more impressive showing of evidence in the Senate than he made in the courts after the election. Otherwise, the result will be to discredit and undermine his own supporters, and probably convince a good number of Republican senators to change their minds and vote to convict.
I actually think McConnell’s spokeswoman’s view is at least as likely: Trump dismissed his expensive lawyers because the outcome of the trial is no longer in doubt and he doesn’t need them.
He did the exact same thing after the election. Within a couple weeks, he fired his professional election lawyers and replaced them with small-time activist lawyers and Giuliani. Conventional wisdom was that they withdrew due to harassment, but I don’t believe it. Instead, I think it was either: (1) A disagreement over strategy because the lawyers weren’t willing to pursue fraud allegations without evidence; or (2) He didn’t want to spend big-firm lawyer money after it quickly became clear that litigation was futile, and instead only spent what he needed to in order to put on a show. Based on their litigation strategy (such as it was), I tend to think it was the latter.
There’s also the question of who has actually been paying for the lawyers. I don’t think Trump is paying them out of his own pocket.