The Republican Establishment used to be a mild and weak alternative compared to the Democrats. The Bushes and McCain always were closer to the Democrats then they should be as a opposing party. There were no real differences between them and the Democrats when it goes to policy.
The establishment leaders in both parties were generous in promising ordinary voters the world and then executing nothing or doing the exact opposite of what they promised.
Now Romney is playing the pro-Democrat game. He attacked Trump for asking to look at the role of Biden's son in the Ukraine, knowing full well that Biden used a loan facility of the US to the Ukraine to fire a prosecutor investigating corruption in the Ukraine. One wonders whether Romney does not realize that what was done resulted in money-laundering in Dollars - a crime that is not allowed anywhere in the world and there are indeed question marks as to why Biden blackmailed the then Ukrainian President to fire the guy if there was not another motive behind it.
Biden now claimed he never discussed his son's business dealings with him - which is an obvious lie. The other story is that -
* there were other countries who wanted the said prosecutor out - not only the USA; and
* that the Prosecutor was not investigating the Ukraine company for whom Biden's son was a Consultant - where that came from nobody knows - the prosecutor was investigating all potential corruption cases; and
* that Biden Junior resigned as Director in 2015 and that Biden's visit to Ukraine was in January 2016 and there could have been no family involvement in the ultimatum Biden put to the then Ukrainian President.
The latter is a hollow statement. If there was any criminality involving Biden Junior there is no way that the issue could not be investigated after Biden Junior's departure from the firm. His departure does not necessarily mean that he was absolved at all in wrongdoing while he was working for the firm in question.
The other issue is that Biden Junior had no experience of working as a Consultant for a Gas and Petrol company and the question arises what was he in fact paid for. The hole process seems fishy to me.
As to the Romney issue it is not surprising Romney - like the Bushes - are against Trump - but will that means the destruction of Trump? I doubt it very much. The distrust amongst voters about the wheeling and dealing of the Washington Establishment - both Democrats and Republicans - is as clear as it was in 2016.